The 42" one's I have seen were showing for up too a 90lb dog. Be safe and get the larger one. As was just stated, Make sure it has a divider to expand the size of the crate to your puppy's needs.
Bella 10-31-2012 Shepherd/mix rescue
Zoe 11-21-2012 GSD
Moe. 10-1 -2013 GSD