In my experience the old French concrete cages are the best. They are a good size (done correctly, two or three interlocking cages per rabbit, side by side).
Also the French metal cages on wheels. Bunny goes in and the cage can be wheeled gently over the grass so they can have fresh grass without having to take them out, the cage is covered on one side and above to give protection against wind/rain and even have a little 'shelf' inside so bunny can hop up off the grass. Fox proof and totally fab - expensive though - over 240e!
If anyone wants to see what they look like I'll try and pop some sort of pic on this page.