Thank you for the reply! Just to clarify, those two log outputs are both from Wasabi, one doing a server side copy within a bucket (faster) and one doing a server side copy between 2 buckets (slower). The B2 log output I was comparing these with is the one given in my original post, which does look quite different. However, I did a test again with the exact same files, doing a server side copy within 1 bucket (since B2 can't copy between 2 buckets afaik), and here is the comparison:
Wasabi:
/path/to/rclone/bin/rclone copy :s3:bucket-name/folder1 :s3:bucket-name/folder2 --s3-access-key-id XXX --s3-secret-access-key YYY --s3-region eu-central-1 --s3-endpoint https://s3.eu-central-1.wasabisys.com --s3-provider Wasabi -vv --stats 1s --stats-one-line
2019/08/06 16:19:13 DEBUG : rclone: Version "v1.48.0" starting with parameters ["/path/to/rclone/bin/rclone" "copy" ":s3:bucket-name/folder1" ":s3:bucket-name/folder2" "--s3-access-key-id" "XXX" "--s3-secret-access-key" "YYY" "--s3-region" "eu-central-1" "--s3-endpoint" "https://s3.eu-central-1.wasabisys.com" "--s3-provider" "Wasabi" "-vv" "--stats" "1s" "--stats-one-line"]
2019/08/06 16:19:13 DEBUG : Using config file from "/path/to/rcloneconf/rclone.conf"
2019/08/06 16:19:14 INFO : S3 bucket bucket-name path folder2/: Waiting for checks to finish
2019/08/06 16:19:14 INFO : S3 bucket bucket-name path folder2/: Waiting for transfers to finish
2019/08/06 16:19:14 INFO : test1 (4th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (5th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (6th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (3rd copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (7th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (8th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (9th copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (another copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1 (copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test1.pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test2 (3rd copy).pdf: Copied (server side copy)
2019/08/06 16:19:14 INFO : test2 (4th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (5th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (6th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (7th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (8th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (9th copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (another copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2 (copy).pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2.pdf: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (3rd copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (4th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (5th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (6th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : 1.414G / 1.549 GBytes, 91%, 1010.244 MBytes/s, ETA 0s (xfr#24/32)
2019/08/06 16:19:15 INFO : test3 (7th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (8th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (another copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (9th copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3 (copy).zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test3.zip: Copied (server side copy)
2019/08/06 16:19:15 INFO : test1.txt: Copied (server side copy)
2019/08/06 16:19:15 INFO : test2.txt: Copied (server side copy)
2019/08/06 16:19:15 INFO : 1.817G / 1.817 GBytes, 100%, 1.101 GBytes/s, ETA 0s
2019/08/06 16:19:15 DEBUG : 28 go routines active
2019/08/06 16:19:15 DEBUG : rclone: Version "v1.48.0" finishing with parameters ["/path/to/rclone/bin/rclone" "copy" ":s3:bucket-name/folder1" ":s3:bucket-name/folder2" "--s3-access-key-id" "XXX" "--s3-secret-access-key" "YYY" "--s3-region" "eu-central-1" "--s3-endpoint" "https://s3.eu-central-1.wasabisys.com" "--s3-provider" "Wasabi" "-vv" "--stats" "1s" "--stats-one-line"]
B2:
/path/to/rclone/bin/rclone copy :b2:bucket-name-test/folder1 :b2:bucket-name-test/folder2 -vv --stats 1s --stats-one-line --fast-list --transfers 14 --b2-account XXX --b2-key YYY
2019/08/07 08:22:26 DEBUG : rclone: Version "v1.48.0" starting with parameters ["/path/to/rclone/bin/rclone" "copy" ":b2:bucket-name-test/folder1" ":b2:bucket-name-test/folder2" "-vv" "--stats" "1s" "--stats-one-line" "--fast-list" "--transfers" "14" "--b2-account" "XXX" "--b2-key" "YYY"]
2019/08/07 08:22:26 DEBUG : Using config file from "/path/to/rcloneconf/rclone.conf"
2019/08/07 08:22:31 INFO : B2 bucket bucket-name-test path folder2/: Waiting for checks to finish
2019/08/07 08:22:31 INFO : B2 bucket bucket-name-test path folder2/: Waiting for transfers to finish
2019/08/07 08:22:32 INFO : 0 / 1.110 GBytes, 0%, 0 Bytes/s, ETA - (xfr#0/32)
2019/08/07 08:22:33 INFO : 0 / 1.110 GBytes, 0%, 0 Bytes/s, ETA - (xfr#0/32)
2019/08/07 08:22:33 INFO : test1.txt: Copied (server side copy)
2019/08/07 08:22:34 INFO : 66 / 1.047 GBytes, 0%, 8 Bytes/s, ETA 36100h35m21s (xfr#1/32)
2019/08/07 08:22:34 INFO : test1 (3rd copy).pdf: Copied (server side copy)
2019/08/07 08:22:35 INFO : 53.149M / 1.036 GBytes, 5%, 6.160 MBytes/s, ETA 2m43s (xfr#2/32)
2019/08/07 08:22:35 INFO : test1 (8th copy).pdf: Copied (server side copy)
2019/08/07 08:22:35 INFO : test1 (another copy).pdf: Copied (server side copy)
2019/08/07 08:22:35 INFO : test1 (7th copy).pdf: Copied (server side copy)
2019/08/07 08:22:35 INFO : test2 (5th copy).pdf: Copied (server side copy)
2019/08/07 08:22:35 INFO : test2 (6th copy).pdf: Copied (server side copy)
2019/08/07 08:22:36 INFO : 340.967M / 1.004 GBytes, 33%, 35.414 MBytes/s, ETA 19s (xfr#7/32)
2019/08/07 08:22:36 INFO : test2 (3rd copy).pdf: Copied (server side copy)
2019/08/07 08:22:36 INFO : test1.pdf: Copied (server side copy)
2019/08/07 08:22:37 INFO : 458.301M / 1.052 GBytes, 43%, 43.122 MBytes/s, ETA 14s (xfr#9/32)
2019/08/07 08:22:38 INFO : 458.301M / 1.052 GBytes, 43%, 39.413 MBytes/s, ETA 15s (xfr#9/32)
2019/08/07 08:22:38 INFO : test2 (7th copy).pdf: Copied (server side copy)
2019/08/07 08:22:38 INFO : test1 (4th copy).pdf: Copied (server side copy)
2019/08/07 08:22:38 INFO : test2 (4th copy).pdf: Copied (server side copy)
2019/08/07 08:22:38 INFO : test2 (9th copy).pdf: Copied (server side copy)
2019/08/07 08:22:38 INFO : test2.pdf: Copied (server side copy)
2019/08/07 08:22:39 INFO : 768.192M / 1.019 GBytes, 74%, 60.832 MBytes/s, ETA 4s (xfr#14/32)
2019/08/07 08:22:39 INFO : test2 (8th copy).pdf: Copied (server side copy)
2019/08/07 08:22:40 INFO : 832.377M / 1.014 GBytes, 80%, 61.078 MBytes/s, ETA 3s (xfr#15/32)
2019/08/07 08:22:40 INFO : test1 (6th copy).pdf: Copied (server side copy)
2019/08/07 08:22:41 INFO : 885.526M / 1022.980 MBytes, 87%, 60.536 MBytes/s, ETA 2s (xfr#16/32)
2019/08/07 08:22:41 INFO : test3 (4th copy).zip: Copied (server side copy)
2019/08/07 08:22:41 INFO : test2 (another copy).pdf: Copied (server side copy)
2019/08/07 08:22:41 INFO : test2.txt: Copied (server side copy)
2019/08/07 08:22:41 INFO : test2 (copy).pdf: Copied (server side copy)
2019/08/07 08:22:42 INFO : 1.057G / 1.057 GBytes, 100%, 69.274 MBytes/s, ETA 0s
2019/08/07 08:22:42 INFO : test3 (8th copy).zip: Copied (server side copy)
2019/08/07 08:22:42 INFO : test1 (9th copy).pdf: Copied (server side copy)
2019/08/07 08:22:43 INFO : 1.176G / 1.176 GBytes, 100%, 72.438 MBytes/s, ETA 0s
2019/08/07 08:22:43 INFO : test3 (another copy).zip: Copied (server side copy)
2019/08/07 08:22:43 INFO : test3 (6th copy).zip: Copied (server side copy)
2019/08/07 08:22:43 INFO : test3 (9th copy).zip: Copied (server side copy)
2019/08/07 08:22:44 INFO : 1.378G / 1.378 GBytes, 100%, 80.025 MBytes/s, ETA 0s
2019/08/07 08:22:45 INFO : 1.378G / 1.378 GBytes, 100%, 75.729 MBytes/s, ETA 0s
2019/08/07 08:22:45 INFO : test3 (copy).zip: Copied (server side copy)
2019/08/07 08:22:45 INFO : test3 (3rd copy).zip: Copied (server side copy)
2019/08/07 08:22:45 INFO : test3 (5th copy).zip: Copied (server side copy)
2019/08/07 08:22:46 INFO : 1.579G / 1.579 GBytes, 100%, 82.375 MBytes/s, ETA 0s
2019/08/07 08:22:46 INFO : test3.zip: Copied (server side copy)
2019/08/07 08:22:47 INFO : 1.646G / 1.646 GBytes, 100%, 81.713 MBytes/s, ETA 0s
2019/08/07 08:22:48 INFO : 1.646G / 1.646 GBytes, 100%, 77.935 MBytes/s, ETA 0s
2019/08/07 08:22:49 INFO : 1.646G / 1.646 GBytes, 100%, 74.491 MBytes/s, ETA 0s
2019/08/07 08:22:49 INFO : test1 (5th copy).pdf: Copied (server side copy)
2019/08/07 08:22:50 INFO : 1.698G / 1.698 GBytes, 100%, 73.588 MBytes/s, ETA 0s
2019/08/07 08:22:51 INFO : 1.698G / 1.698 GBytes, 100%, 70.600 MBytes/s, ETA 0s
2019/08/07 08:22:51 INFO : test3 (7th copy).zip: Copied (server side copy)
2019/08/07 08:22:52 INFO : 1.765G / 1.765 GBytes, 100%, 70.527 MBytes/s, ETA 0s
2019/08/07 08:22:53 INFO : 1.765G / 1.765 GBytes, 100%, 67.878 MBytes/s, ETA 0s
2019/08/07 08:22:54 INFO : 1.765G / 1.765 GBytes, 100%, 65.421 MBytes/s, ETA 0s
2019/08/07 08:22:54 INFO : test1 (copy).pdf: Copied (server side copy)
2019/08/07 08:22:54 INFO : 1.817G / 1.817 GBytes, 100%, 66.032 MBytes/s, ETA 0s
2019/08/07 08:22:54 DEBUG : 7 go routines active
2019/08/07 08:22:54 DEBUG : rclone: Version "v1.48.0" finishing with parameters ["/path/to/rclone/bin/rclone" "copy" ":b2:bucket-name-test/folder1" ":b2:bucket-name-test/folder2" "-vv" "--stats" "1s" "--stats-one-line" "--fast-list" "--transfers" "14" "--b2-account" "XXX" "--b2-key" "YYY"]
So B2 is the slower one but the stats do look quite similar. Apologies, I should have done the test with the same data to start with... For interest sake: how does rclone estimate the total data to be copied in this scenario?