Which incubator to buy!?

I am wanted to breed my chickens and sell their offspring, but as I haven't ever hatched chicks with an incubator before, I have no idea which to buy. I usually just let my broody hens get on with it!
So I either have the choice of buying a 24 egg automatic incubator at £98.00 or buying a 56 semi-automatic egg incubator for £109.00.
The 56 egg incubator, though, people have said doesn't work sometimes and the temperature and humidity are different in each corner.
Do you think, as I am a beginner in using an incubator for eggs, that I should get the 24 egg incubator, so I am not overloaded with chicks?Or should I just go for it and get the 56 egg incubator??
Thanks in advance!!!