They are much livelier and also have a more rapid song.
Have been compared to waxbills, which I find kind of right.
Try and get some to judge for yourself!
Someone should really look up if they are still available in the US, the Q had already been raised a few times.
Or... visit with deep pockets and buy as many as you want for $4/pair!
I have bought a 2nd pair recently myself.
The standard US page on Timor zebras:
http://www.efinch.com/species/timor.htm