Digimon. basically because each seaosn there's a bit more of a story behind each one, not to mention you have a few cases of major character development - one example in Ken from series 02 (I know it's his dub name but I for the life of my can't remember the original japanese one) who was at first this bad guy calling himself the Digimon kaiser and wanting to control everything, however he got the crap beat out of him by one of the heroes and even saw the error of his ways, thus making a huge change from going from a major antagonist to that of atonement where Ken rights his wrongs by being on the good side throughout the rest of the story.
don't get me wrong; at first, Pokemon was also great, and I still love the games and whatnot..but as far as the anime version's concerned...I just lost interest over the course of time. it just got too repetitive. ash wins a battle; moves further to his goals. goes to a gym, gets his arse handed to him, learns from the defeat, goes and trains to become stronger, come back and beats the gym min a rematch, moves on, catches a pokemon, moves on to the next town, gym, eventually league before going home then setting out again to a new region, repeat, repeat.
There's character development too, but unfortunately it comes in the forms of the other characters leaving the show, then coming back in later arcs only to drop off the face of the series permanently save for team rocket..
so yeah. that's my two cents in which i think Digimon anime is better than the Pokemon Anime. Hope nobody takes offense; I just felt like being honest on the whole thing.