I've only played Digimon World Dawn/Dusk but, as far as I'm concerned I think they are both great in their own respects. I praise Digimon for its dazzling Digimon designs, that I find very attractive, buuuuttt... This is where I think Pokemon fails a bit. I honestly believe Pokemon has gotten a little lazy with the design in Pokemon white/black. The new generation Pokemon look well... a little... dull, maybe?
Now, If you want to go into the actual game-play, I like Pokemon (then again like I said, I haven't played too many Digimon games) I think the combat is smoother and much more enjoyable Digimon was a little repetitive.
But like I said, they both are pretty great :D