I have been with guys who always get off from a blow-job, and guys who find it harder. But I have, so far, always managed to get them off, despite any difficulties. They key is determination and awareness. I, on the other hand, find it very hard to get off when I'm given oral. I can count on one hand how many times I got off through oral. So, I think guys have a pretty hard job, with me at least. But, I can't say I've worked any less harder on the reverse of it.
I'm going to say that girls have a tougher job (I never heard of guys gagging during oral) but they whine about it less
