For me? Hands down (or in?), receiving anal. Which is not to imply that giving oral is not, butt comparatively, giving oral is almost foreplay. i qualify "almost" because sex for me ideally (vitally?) is the symbiotic blending of need/desire between two guys. I.e., if He loves receiving oral, but is not into anal, i have desire/need in me to pleasure and release a Man both ways that i can easily connect to His need/desire that way. Just because anal is ultimate for me, doesn't make it exclusive for me.
It's a lot more complex though. i don't think there is such a thing as 'just sex,' which i think often translates into an attempt to keep sex as "just" physical. i think it's connected to our intellectual and emotional self as well, though i know a lot try to fragment it, or simply are not aware or integrated. i want and love what i perceive as holistic sex. For me, sex is a vast, infinite topic lol.
Anal for me has the potential to connect to and bond with another in more ways, physically, intellectually and emotionally. "Mind fuck." Though, again, so much is in play here. One of the most profound mind fucks i've experienced was giving oral to a Man Who managed to regress me using 'just' oral between us. Still, in my imagination, had He been equally anally penetrative, it would have been even more profound as i'm wired.