Everyone has their own opinion on what size is better for breeding. Some say smaller because its easier food distribution for the fry. Others say larger so the fry have more room. I am in the middle camp myself. I am going to be breeding in 15 gals large enough to give the fry room, and small enough to feed easy. Also an easy size to clean when I need to.
Really its not the size of the tank but how you take care of the water changes. I just read that one of my favorite breeders spawned and is actually growing out fry in a 5 gallon tank, removing the males as they show themselves. Gorgeous, big fish so far too :)
Bigger tanks are preferred for grow out because it's easier to control water quality, with less stress. You can skip a day of water changes and not worry about ammonia, etc, levels whereas in a small tank you have to be on top of it 100% of the time.
I've said it before and I'll say it again. Personally I like to spawn in a smaller tank. Not only for the fry but IME with just spawning in 10 gallon tanks is the pair seems to lose each other too easily for my taste and it takes longer. In my 4 gallon tubs they can still hide but don't stay apart as long as they did in the 10 gallons.
Then again OFL has spawned in like 75 gallons... different strokes for different folks.