I prefer subs over dubs but there are good dubs out there. When I was relatively fresh to anime, I preferred dubs but there weren't too many around so I started picking up subs. I still liked dubs more though for a long time because subs were an ugly yellow and blurry. Honestly, it all changed when I bought an HDTV in the mid 2000's. Finally, I could read the subs without having to sit 3 feet from the screen. At a distance, I could easily read the subs and still absorb the action occurring on screen. These days, I usually pick the sub track, but occasionally, I'll check out the dub track to see if it's acceptable. Odd as it might sound, I can adapt to dubs easier when the setting for the anime is not Japan. So, I can watch a fantasy dubbed with less resistance than something set in a Japanese high school.
One thing I've enjoyed doing lately is re-watching old animes I loved dubbed, but this time subbed. When I revisited The Slayers franchise last year, it was a series I'd seen a dozen times but I almost always watched it dubbed. So, this most recent time, I watched it subbed and it was like it was a fresh new show. The dub of Slayers is great (well a minor complaint about Amelia since the dub changes actresses halfway through the first season), and I recommend it as a respectable example, but watching it subbed was invigorating. I'm planning on reacquainting myself with Neon Genesis Evangelion soon and watching that subbed. I've seen that one a lot, too dubbed but subbed maybe partially once. It should be fun. Love Hina's another on my list.
I will watch whatever is available, however with my eyesight deteriorating in recent years, I find myself searching more and more for dub versions because it's becoming just too difficult to read subs. also, sometimes i actually prefer dub voices to the original japanese voices... :) p.s. scratched corneas blow.
I prefer subs since I think the voice acting is above trash can quality on a regular basis. Bleach is especially bad imo since they seem to have decided that Aizen's voice should be that of an angsty homosexual, which is the total opposite of what is should be imo.
I prefer dub alot of times the japanese counter part seems like it has a voice that is too child-like I watched FMA brotherhood in sub and am watching it in dub and I can tell you the show sounded way better with Vic Mignona to me Ed in the japanese version sounded like he did not even hit puberty.
hebrew dubz are the best I have seen so far, I used to watch anime either subed, or dubed in arabic or hebrew, but the first time I thought about watching some of my favourite animes in engish dub, I was just horofyed of the awfulness(voices, acting,...), personally, the only good english dub I have ever seen was DEATHNOTE, it's the only one that can be compared to it's japanese version in my openion.