Don't neccessarily agree it's harder having done both, flying the FAA test floppy stick is no walk in the park. They are just different.
But what there is is a heap load more pressure, if you fail the JAA in a twin it's probably around £4k minimum for a retest, Faa it's a couple of hours at $250 per hour.
The extra financial pressure as a result really messes with peoples heads and makes it appear much, much harder, with significantly more pressure.
Enjoy