I agree with jjroland, V3 & V4 but want to add that Aiko3 is also a really special model to use.  Wonderful morphs here and around for Aiko 3.

I use V3 and Aiko3 only because I have more morphs between both of them in my stash of stuff.

If I did not have V3, I would purchase V4 only because I know eventually she will have as much as V3 in the very near future.  Why go backwards when you can go forward.

Sharen

PS: I guess your wallet will determine your direction also.