I've only had Platys, so I can't really say. They've been easy to breed though...put them in a tank together and viola! you have fry! A friend of mine has Guppies and she always has lots of fry.
guppies are the easiest for me. i've breed guppies and mollies frys at the same time and the guppies seem to grow 4 times faster than the mollies. don't know the reason behind that but i'll find out.
i didnt intend to breed my fish, but all of the sudden there were fry! i didnt net them or move them to another tank, but the hardy little suckers are still alive. way to go platies!
my swordtails are forever at it....luckily they eat their young more than the others, so I dont get over-run....ahh well all that is over and done with now...finally managed to find a new home for my livebearers! YAY!
guppies defo i would say had 4 batches from them now
had 1 fry from a balloon molly then ther fish died,
had platy fry for the first time this week, but i would say mollys are the hardest to breed well balloon mollies ne ways