Okay, if you are looking to for the easiest to breed, live bearers will be your go-to fish. Guppies, Mollies, Platys, Swordtails are among the easiest to breed of any fish.
On the other hand, give two convicts a tank and water and they will do their thing, no questions asked. AND they care for their babies.
There is no better one to get. I like mouth brooders my self, but that's because I like the challenge.