Livebearers are great, but in too many cases, it's all too easy to wind up with overpopulation problems, especially once every possible home/store has been saturated with little cuties.
With egg layers in a community tank, it's such a pleasant surprise when one or a few fry, quicker and more fortunate than the rest, survives - and much easier to provide homes for them within one's own tanks.
Of course, I speak only as an accidental breeder with limited (sniffle) room...
If I won the lottery and had the sprawling, cement-slab-based home of my dreams, the one with the automatic water-change system and whatnot, there are a number of interesting livebearers I wouldn't mind having, but not in my current limited circumstances.
So - tough call...