I voted for Platys because I've only kept them and swordtails. I found that my swordtails are pretty mean, which is not what I want for a community tank.
Also consider goodeids or some of the many "native" livebearers like Heterandria and Girardinus types. Each group has their own strategies and requirements, and the folks who figure it'll be a snap because they've had success with guppies and mollies will be greatly surprised.
Anableps (four-eyes) are only for the most dedicated of hobbiest. Definately not for the average aquarium keeper, and definately not for the folks repeatedly asking how to tell if their guppy is pregnant.
I voted for Platys because I've only kept them and swordtails. I found that my swordtails are pretty mean, which is not what I want for a community tank.
alot of people like platys but to my expierance mollys are more hardy and wil live under harder conditions ......swords on the other hand(which u didnt post) are my FAVORITE they are definately there own fish but can be relatively agressive (inlike most others) and are a breed for a few reasons but if you have a small tank with some bottom feeders get a few of these !!! (they usually go well with most fish but space becomes an issue)
I have gups, swords, platy, and mollies....I love my mollies because there personality, I have mollies in a tank of there own and swords gups and platy in a tank of there own. I can pick up my mollies and they r not a bit scared of my hand in the tank...The other run when u walk up to the tank. Mollies is the best.....
I voted for guppies because i think you can get the most variety of colors and markings from them. I have seen some neat platties and Mollies, but I haven't actually raised any live bearer besides guppies and Endler's. In fact that's where I get the name "gupler" I have mostly hybrids now and they are fun. (interesting tail shapes) I've read just enough about four eyes to think they would be fun to try some time, but I don't have the space for them right now.