3catsoo, that really becomes a tricky question and one which may be difficult to answer without sounding graphic.
ok, here goes. I personally have a suspicion that the coming on face thing is a fairly recent (relatively) speaking phenomenon, fuelled by porn. Pornography focuses so much on ejaculation, or the cum-shot as they call it, and there are millions of web pages out there dedicated to that one thing. I am not saying that historically men never came on a woman's face but I do think it has been glamourised in the last 15 years.
I think to answer the question fairly, you really have to know what dynamic is going on at that moment. If you are acting out a whole "whore" scenario, which both parties are party to, then coming on the woman's face or body can actually be a real turn-on for both as it feeds into the whole "treating them like meat" type role play. And before anyone flames me for that, I do not mean it in the literal sense. Everyone in sexual relations sometimes plays at just being totally dirty.
If however it is in the context of really connected love making, clearly it is neither wholly appropriate nor, in reality, much of a turn on.
It is also a question of environment too. I mean, if you are giving your partner surprise oral sex where you have not prepared tissues, swallowing is the most practical solution.
hmmm, I am not sure that really answers your question either way! I guess all I am saying is there is a place for everything in a consensual context. Bad cliché but it is horses for courses.
And I repeat what I said earlier, if the foreplay is good, it doesn't matter where or how you come. Mind you, I say that with one caveat - it can be a real turn off for a man if he feels that in some way he has to inhibit himself when coming. By that I mean, if he feels that his partner does not like it when he comes or will feel disgusted, it really can be a turn off. If that is the case, it is best not to engage in anything other than ejaculation during full sex. What I mean is that much of the fun of making your partner come either with your hands or mouth is that you can control the pace and really work, literally, to a climax. If that climax feels in any way held back, it can lessen the pleasure for your partner.
Once again, I hope that makes sense! I am trying to maintain a correct tone...