I have 2 hamsters right now and they each have a 20 gallon tank. Another reason I like tanks is that they have better ventilation (the habitrail house was kind of stinky) and they are much easier to clean.
I get the impression they are better for one of the species of dwarf Hamster than for Syrians.
This is Pants the day I got her when she was about 3 weeks old and not too big for her house yet.