Ah, the age-old question. It really depends. I definitely love the original Japanese version, but that's for nostalgic reasons. Plus, since Funimation basically turned Dragon Ball, Dragon Ball Z, Dragon Ball GT, and the movies into a different thing entirely, I can watch and appreciate both. The Japanese version for anything before that "Son Goku and His Friends Return" TV special, is great and is Dragon Ball.
However, that dub has its own place in my nostalgia bank, so to speak. It's easy for me to separate the two and view them as two separate entities that I can enjoy; this separation was made possible by just how far off the rails Funimation took the series. Actually, I've recently come across the Ocean/Westwood/Blue Water dubs for all three original series so it's like I have three separate versions to enjoy. Even moreso, since I'm trying to learn Spanish, I also have DB/Z/GT/movies/etc. in Spanish, so I get to enjoy it four times over, each with their own nuances.
But I'm no big anime purist and I'm about as casual of a fan as you can get. Thus, as the dub is more faithful now, I don't feel the need to watch it in Japanese. I find it really convenient to just throw Kai on and have it in the background while I do something instead of having to sit there and read the subtitles. That's what I appreciate about it. I feel that with Kai and onward, just because of how they did the dub, I don't have any interest in seeing the original version. I actually like the voices and all, but there's no reason for me to have to pay attention to everything that's written, I have things to do. I am dipping into Japanese slowly but surely (it'll take forever), so maybe -- just maybe -- one day I'll get to watch the Japanese version without reading and without relying on someone else's translations.
