I am considering building me one or the other of these two chamberings. I own four 6.5X55's and would really like to try an AI version. Anyone know the difference in these two chamberings? Any suggestions? I'll be building on a M98 Mauser action.

I doubt there is a significant differance between them. I would look into the reloading die availability for each, then go with the one you can get dies for the easiest.