And it’s not even a fair comparison; eventers to jumpers is far more equitable, and pretty close in style. The kind of jump you want in an eventer is NOT the kind of jump you want in a hunter–big flashy, hanging in the air jumps don’t have any advantage on XC, and actually slow you down and tire out the horse faster, which isn’t something you want in a timed event where the horse has to then recover and then go showjump. So riding in a style that produces that kind of jump, or claims to produce that kind of jump, has absolutely no purpose. I guarantee, if had some kind of advantage, and you wouldn’t go arse over teakettle down a drop, people would be out on XC riding that way too.
Plenty of riders switch back and forth–I consider myself an eventer now, but I did a hunter show two weeks ago. But most eventers who cross train (and most do!) go do jumpers, and I’d guess in most cases you wouldn’t notice a difference in the rides between them and a regular jumper rider.