They grow to a good size, 8"-12", and are some what skiddish. So they need a good size aquarium. They also need a good amount of greens otherwise they'll waste away. So unless you tank has a lot of algae you're going to need to feed them.
They're all reef safe but Siganus magnifica will pick at sps.
For the most part they tend to be reef safe. I had seen my Foxface Lo pick at some sps before but nothing too major. Like Marrone said, they are very skiddish and will bolt if spooked. It's just a nice addition instead of tangs, serves the same purpose for algea removal.
The Fuji Foxface is just like the others. It's some what rarer than the others and usually it only comes in larger size, unlike the other Foxfaces where smaller size are usually available.
New World does have some smaller ones, about 3"-4", which are about the smallest I've ever seen.
They're all about the same. They do very well but are skiddish and need space in the tank. They eat a lot of greens and shouldn't be place with very aggressive tank mates.