I watched both as a kid and as an adult. Pokemon seemed to be just a string of overdramatic.. drama and stupid fluff the other times. It was par for the course, but still not really fufilling for me at any age.
I prefer Digimon because, even in spite of its target audience, it's incredibly mature. It almost seems like it was made for a different demographic altogether. And I'm not talking sexualized Digimon or a few hidden innuendos, but subject matter. Some of the arcs and moments in the episodes were extremely emotionally evocative, and they went over my head entirely when I was younger. Only when I went back and rewatched them when I was older did I understand. And I was impressed, even.
I'm not saying the Pokemon anime was BAD, really, it just was relatively par for the course. Which I guess they should be congratulated for, because that was where their sights were set. Digimon went on to impress, however, going above and beyond.
Of course, as far as the games go, there's no competition whatsoever. Pokemon wins by a long shot.
...actually, come to think of it, there were a few hidden innuendos in some parts of Digimon. Hrm.