Performance? iperf measurements representative of real world data?

[rcfa]

I used, until yesterday, an IPSec site to site link to tunnel just about all my traffic.
Then I played with OpenVPN and did some performance testing with iperf :o

iperf -c 123.45.67.89 -i 10 -fK -n 1024M

IPSec: (AES 256 GCM) [lower levels of encryption improve performance only marginally]

[  3]  0.0-697.0 sec  1048576 KBytes  1504 KBytes/sec

OpenVPN: (unencrypted)

[  3]  0.0-221.8 sec  997888 KBytes  4500 KBytes/sec

OpenVPN: (AES 128 CBC)

[  3]  0.0-263.8 sec  857856 KBytes  3252 KBytes/sec

Questions:

• Does anyone know if iPerf just produces atypically compressible data, or is OpenVPN really THAT much faster?

• What's the fastest/best performing compression? Don't really have any relevant unencrypted data on the link, since it's simply a routing tunnel, I just need things encrypted enough that some ISP doesn't get the idea to to do content filtering or stuff like that, so even a simple fixed-key XOR would be good enough, but the performance gains with the unencrypted link are inspiring…

Still shocked by these numbers....