I grew up with both and love many of each, but while I've largely stopped watching Western cartoons I still watch at least one anime per season. I find that when I do want to watch Western Cartoons, it's more of the ones I've watched before (nostalgia) and not exactly wanting to see what's out there. Anime just seems to surprise me at times with the things they bring out. I also play a lot more games with anime adaptations, so that's also influenced my watching habits as well.
Admittedly I really haven't given Western Cartoons as of late a chance (and there are some really good ones out there from what I hear), but seeing some of what I do love deteriorate over time (or end inconclusively) makes me not want to venture back... (Not that that isn't a problem in long running anime as well, but I guess I've been more disappointed by Western cartoons. Might also be that I haven't been choosing the wrong anime or that I keep choosing the wrong Western Cartoons in itself.)