There are so many hutches like this around... as to whether it is big enough, it seems to depend who you ask!
A lot of the pet shops sell hutches that are really small (3 feet). but on the other end of the scale I looked into adopting a rabbit from a shelter around here and they have a minimum requirement of 2m x 2m x 1m which is pretty massive. the hutch my boyfriend is building is 1.5m x 60cm x 60cm roughly from memory. so um what is big enough seems to depend...
this is probably a pretty obvious thing to say but the good thing about the double story ones is that you get twice the room for the length... if you know what I mean. but a double story hutch isn't an option for me because my boy bunny is disabled and wouldnt be able to get up the skinny ramp.