Cage size needs to be considered along with out-of-cage exercise time. If bunny will be getting about 5 hours outside of the cage, then it is large enough. As a square it is about 16 sq ft. As a rectangle it's about 12 sq ft. Neither of those sizes are sufficient unless there is out-of-cage time for binkies and dashes.
If you use a wall as part of the cage (as Poopy Poo mentioned), then the area can easily become 30 sq ft and plenty of space even without time out of the cage.
Here is an example of a cage that makes use of part of a wall.
I also agree that it wouldn't do to get the lower height. Get the medium or taller one.