Subs are cool, dubs are cool, but sometimes the dubs can get pretty goofy with the voices and it just makes it hard to watch.
Case in point, Ergo Proxy. I started watching it subbed, and then decided to try the dubbed version a few episodes in, and it was a joke. They gave Re-l's entourage(personal robot) one of the silliest voices I've had the mispleasure of hearing. I switched back to subbed and kept on my merry way.