I'm a fan of both, but I think the strength of Digimon's designs stems from their variety. Digimon has a lot more freedom to have some really wild and out-there designs, ranging from cute friendly pink blobs to giant metal dragon made of guns to little red riding hood with molotov cocktails to demonic incarnation of lust with big boobies. You can look at any of them and think "yup, that's a digimon alright." Pokemon feels a lot more strict.

Digimon has a literal pile of shit with a goofy mouth and gangly arms and everyone loves it. It's a memorable design that people like because it's so unique. Pokemon has trouble taking that kind of risk.