I really couldn't answer due to first, as someone mentioned, a BJ is sex and second, if by your question you mean vaginal sex vs. oral sex, then it depends on different factors.
I enjoy oral due to the fact it usually gives me more intense orgasms then penetration and allows me to be more passive and fantasize more. Also it sometimes actually seems more intimate than vaginal since it feels like the woman is totally accepting you if she swallows. Besides my wife, only one other woman has finished me off in that way and then only because with the others I used oral more as foreplay than the actual main course.
Penetration on the other hand has it's own pleasures and despite the opinions of some, each vagina has it's own unique feel to it on my penis much more than a mouth. It gives me a different sense of intimacy than oral, more emotionally than physically oriented and more akin to "making love". There also is a more primal instinct feeling of coming into a woman that way even if you know it will not result in pregnancy. Because of the uniqueness of each vagina, I consider it the piece de resistance of a woman and being able to get into her pussy the ultimate goal in a sexual situation. This was one of the reasons that when we were swinging, I used oral only as a warm up and would stop them from continuing when I started getting too turned on and we'd switch to penetration least I pop in her mouth and then never get a chance to experience her pussy since a lot of our encounters were "one and done" and I'd likely never get to play with her again.
So the choice is kind of like apples and oranges.
