From a practical viewpoint, I'd have to give it to Bloody. Why? The Arm blades for one, she had reach and can control more space than Buffy. Buffy gets points because she doesn't have to stop to "refuel" [per Video game] but being human, even superpowered, Buffy will get tired and run out of energy...and in this sort of a matchup, the first one to tire would be the loser.
Now...here's a question: Would Bloodrayne be considered the winner if instead of killing Buffy, she beat her up, then took her out to dinner, then back to her crypt...after all, Buffy doesn't object to room-temperature "Special Friends"...there were two of them, in fact...Angel and Spike. Buffy could even "hate herself in the morning...." like she did so well on T.V.
