Well, I'd say that gerbils are more active than hamsters. Also, they are faster, not as fast as mice, but a lot faster than hamters. Gerbils are social, so they need to live in pairs or groups, while hamsters (syrian) have to be kept alone. Gerbils gnaw a lot more than hamsters, so anything plastic in their cage will get destroyed. Gerbils love to dig, so you should give them plenty of bedding.. also it's pretty cool to see them playing with each other. Even though I keep some dwarf hamsters in pairs, I don't see them playing with each other and grooming each other as often as gerbils do. Gerbils rarely bite and when they do it's because you did something wrong. I've been bitten by my gerbils twice. Both times it was by a female and while breaking up a fight. I tell you, it's not smart to break up a fight with bare hands.. haha.
In my experience, in both species, males are more easy going than females. 8)