I always go for subtitles - the actor's voice is too big a part of the performance to throw away. Plus, anyone else remember "The Water Margin"?
I've got mixed feelings about this. Sure, it's great to hear the original language & the actor's voice but if there are many dialogue-heavy scenes then you can find yourself missing an awful lot of on screen action as you busily try to keep up with the subtitles.
I've found that all Studio Ghibli dubbing is done to a very high standard by using very high quality actors. Not all films receive the same ***** treatment unfortunately but it can still be the lesser of 2 evils (cue Russell Crowe!).