Actually Alabanza does support multiple FTP users. There is a KB article on how to do it.
Don't get me wrong, I'm not saying one is better than the other, I actually have a server with both (Alabanza and Ultraspeed).
For me, this would be a hard choice, I know Daniel and he is a great guy and their support is great. But Alabanza has great support to, but you wouldn't be dealing with them, you would be dealing with veoweb, which I've heard good things about.
Ok, maybe this is a worthless post, but either way you go, you'll be in good hands. Pick one of those two, don't go with another company. Unless it were me =)