Abilities that provide added mobility are the best in my opinion. Characters like Alicia, Ginebra, Hans and to an extent, Harec all have this sort of extra dimension to them because of their added movement options. This makes them more versatile, stronger and most importantly... more FUN.
I'm not too sure about Doldren however... His has too many drawbacks.
Mikah's Decoy does give her some pretty interesting mobility as well, but it's not as flexible as the other ones I just mentioned.
I'm sort of exploring Mikah myself at the moment so it's very possible there are things I haven't discovered yet.
If I had to name the better character I would say Alicia. But I think Mikah has a lot going for her, too.
Edit: I suppose the POINT is that Alicia and Mikah are different enough from each other that they provide different playstyles. Just becausee Alicia MIGHT be the better character in general doesn't mean that Mikah is bad or any less fun. A lot of people probably prefer Mikah!