I think that the best would be for a Fray tv show, is the perfect way to continue without having to worry about Angel or Spike aging. And it explores something different from either the Angel or the Buffy shows, allowing Joss to be even more creative this time, since he will be able to go into more science fiction territory.
The other option is to have Angel and Spike either die, or turn human in the comics, since the comics take place around 2006, it would allow for the actors to portray their characters in a present show. If another show was made in the present, then my vote would go for Faith.
So that's it, i would like to see a 3rd Buffyverse live action show, and i think it should either be Fray or Faith.