Japanese is the only language in which I ever watch any anime xd While admittedly there are some good English dubs (I've never watched it, but Cowboy Beebop is know for having a good dub), in general the original language is better. I haven't watched the Pokemon anime in a while, but I did try to watch Sun and Moon (and watched in Japanese of course). I ended up dropping it, but not because I didn't like the voices. I just can't stand watching Ash/Satoshi lose to newbie trainers over and over again at the beginning of each season even though his Pikachu should by all rights be lvl100 already and should stomping every battle. Well, and a few other things really. I've watched a ton of different anime, but sadly Pokemon just isn't my cup of tea anymore.
But back on topic, I always prefer Japanese. Besides thinking that the voices are just better overall, dubs sometimes make use of heavy editing and censorship. Even though 4Kids is no longer in the dubbing business (at least I hope so), their dubs were so bad I could never again watch an English dub without cringing a little.
Btw, not saying no one should watch English dubs. Like I said, times have changed, there's no more 4Kids around, and there are some pretty good English dubs out there. I simply can't bring myself to watch an anime (any anime) in anything other than Japanese.