Usually those end up being the same for me. Although I don't usually strongly dislike people with whom I have nothing in common, so spending time with people I strongly dislike would probably be worse.
People you don't like are worse to be with. People you don't have anything in common with may still be able to talk to you about current events.
How much do I dislike this person? I'd probably choose the disliked person, because they can at least make for entertainment. The awkward pauses with someone that you just can't find common ground with, especially if you are realy trying, is far worse for me.
I am a smart a**, so I have fun with people that bother me. I think that would be my preference. That is assuming that I cannot find common ground with the other person. I find that if I sit long enough I can find something that we either: Both Like or Both Dislike.
I would have to say spending time with someone I have nothing in common with would be much worse. At least with someone I don't like I can still make small talk. I have experienced those awkward moments with someone I have nothing in common with and it's bad! lol