So a buddy of mine just picked up a brand new compensated G23. Which got me thinking about Glock...of which I only really know the name and that they are very popular with LEOs. That being said, is there a brief summary of the differences in the generations of Glocks? I see a lot of listings for 1st gen, 2nd gen, etc. How does one make an informed decision? If a person wanted to see what all the hype was about and was looking at a G17/G19....how would you advise them?