Well, that's a bit more complicated than just asking which one.
I can only speak for myself here. The simple answer is that I love to cum anyway he makes me, and as often as he wants, lol.
The more complicated answer is the following.
When he makes me cum via oral, it's very very intense and by far the hardest orgasm of them all.
When he makes me cum via fucking, it's hot, it's wild, it's animalistic in nature. There is something to be said for that, especially if both people are in the mood for that sort of thing. This I feel can also be broken down further into vaginal and anal, again, both can be done while fucking, and both can be equally hot, wild and animalistic.
But if I had to pick probably my over all favorite way to cum it would have to be during love making. While it's not, "fuck me till I'm raw", or "rip the sheets off the bed", or "OMG baby, stick your huge fat cock deep in me and make it hurt" kind of sex, which is fantastic in it's own right, it's different when you cum during love making.
I may not cum as hard through a vaginal orgasm with his penis as I do through clitoral orgasm, (which may I add is quite normal), it's not always about the strength of the orgasm, but often the meaning behind it.
When two people are in love, especially in love, and they can orgasm together at the same time, looking into each others eyes, whispering each others name, moaning in pleasure, softly, and sweetly as you please the other person you love, there is no better orgasm in the world. Nothing as sensual, as fantastic, as special.
So while I love to cum anyway he wants to do it, hands down my favorite will always be missionary position, either him or I on top, slowly riding each other, looking into each others eyes, kissing each other deeply and passionately as we can until we both make each other cum. Actually, this effects us so much it usually makes one of us cry, or both. Lol, crazy as that sounds.
Oy, I so very much miss my man.