I have two dogs that are the same size. One needs the large Ruff Tough, the other could go a size smaller as she curls up in the back using only about half the crate.
Mine never stand up and look out of the crate like they show in that other picture.
So in my opinion and limited experience you choose a kennel size based on need and comfort of the dog. If you can go smaller, great, then you have more room for gear!