I don't watch as much as I used to, lately but if it is a good dub, then ofcourse dub over sub anytime. If it's like the Funi version of Sunabozu, Desert Punk - hell yeah. I find both enjoyable.
I mean, one could argue that you can't get more original than the Japanese, but if you've got a perfectly fine version done in your own language then why not? Then of course would come the disagreements between stuff that should be translated or is 'sacred' and should be left untranslated, like 'Nakama' (I don't agree with that).
To be honest, you often see it commonly among Otakus that the Japanese version and the VAs are some kind of flawless gods.
I watched the Dub of Naruto first, then watched largely the Subs, then switched back to the Viz DVDs I bought. When I wanna keep up with the recent stuff I go sub.
I've never really seen any Dragon Ball (z) subs cus I've found them impossible to find, but I've watched most of it in Dub. Every now and again, I'll stick the Japanese audio track on and give it a listen, and put subs on if the episode has got them. But the Dragon Ball Dub is so well-known now, for all its apparent flaws, I find it endearing - I wouldn't have it any other way.