The determining factor is what YOU like.
All livebearers have pretty much the same pros and cons unless you do something particularly unique -- a show strain of guppies, a rare livebearer, etc. Some guppies are not particularly hardy, some mollies are prone to problems if you don't add salt to the water. Platies are certainly hardy enough and you could choose one variety to concentrate on or just allow them to do what fishies do.
If you're interested in livebearers, you may wish to look into Endlers,
Ameca splendens or other livebearers.