*looks up info on Asura due to lack of familiarity on Soul Eater*
On the surface, it looks like both would be pretty difficult to kill with Asura being a living manifestation of fear comparable to an abstract being and Alucard gaining omnipresence via Schrodinger. However if what I'm reading up on Asura's Madness ability is true, then it has have the potential to mess with Alucard's omnipresence since the ability relies on Alucard mentally acknowledging that he exists and this kind of mind-fuckery has a good chance to screw up his omnipresence pretty badly if he can't properly comprehend himself.
If Madness can affect Alucard, then I'd give the match to Asura. Otherwise, match is a draw since both would be unable to kill one another.