I always like this question, there are the two sides to it who always have their more vocal advocates on other parts on the internet. When in reality most people don't care. I'd say more newcomers to anime prefer dubs, but that's because anime is becoming more mainstream for younger people. The fact is that there is no real answer to this, some subs are better, some dubs are better. It's really a subjective thing entirely.
I personally prefer to watch subbed, but I always give the dub a chance unless it's not available. Subs usually just have a different feel to them, it's an entirely different experience than most subs. However there are some absolutely great dubs out there, some of them beat the subs out of the water.