Vanilla. No contest.
It seems to me that Highlands used to not add biomes but, rather, made everything more mountainous. I would love that. Of course that could just be related to my failing memory.
BoP and EBXL you can turn off all biomes except ones you like, and they have vanilla like biomes that are enhanced. You should try ATG if you like hilly biomes. However it tends to be far too hilly with a lot of small islands. eg. hilly planes.. ?_?