G17 and a 12 gauge are my current HD tools. After some minor research I've become concerned about wall/over penetration regarding 9mm. What do you guys think about the 37 Gen4? http://us.glock.com/products/model/g37gen4 The 21SF? (I wish a Gen4 version existed) http://us.glock.com/products/model/g21sf I appreciate any advice. Thank you.