My impression is that the only figures that have achieved any real longevity are Posette, Vickie and perhaps to a lesser degree, Aiko 3. The rest tend to follow a predictible trajectory from initial enthusiasm to not so much. There was a big debate over whether Antonia etc. would succeed based soley on their superiority, without a huge marketing effort. In retrospect, I think that things would have worked out the same in either case.

Unless its for money, I'd say make what you enjoy most. I'm sure that the folks who use whatever figure(s) you support will be grateful for more content. There always seems to be somewhat of a market for cute, quirky figures - Koshini was all the rage for a while and I still see things fior Kiki. I actually think that a couple of the 3DU figures, Sadie and Cookie got a decent amount of support. Aiko's anime roots probably helped her stick around and even move into a more realistic role. In terms of general purpose realistic figures though, there only seems to be room for one and Vickie shows no signs of relinquishing her crown.

 

 

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken