Personally, I would prefer not to divide. Dividers have their own troubles: risk of cross-contamination, jumping, possibility of aggression, look messy if not done well, reduced room to swim. I would go for one, with a species of small schooling fish.
HOWEVER: check your water hardness and pH first. It's very important to make sure that your fish are right for your water. If you have a high pH and hard water, neons are probably not right for you; male Endlers would be better. However, if you have soft, acidic water, neons would be great.