I've noticed that pbm-speed-test uses gzip as the default compression while pbm has s2.
In order to avoid confusion I suggest pbm-speed-test should use by default s2 as well.
Here are a few tests I've done on a customer env. You can notice the default behavior is the same as gzip. s2 was significantly faster.
$ pbm-speed-test storage --compression=s2
Test started .1.00GB sent in 3s.
Avg upload rate = 319.80MB/s
$ pbm-speed-test storage --compression=gzip
Test started ................
1.00GB sent in 32s.
Avg upload rate = 31.53MB/s
$ pbm-speed-test storage
Test started ..............
1.00GB sent in 29s.
Avg upload rate = 35.18MB/s