I am looking at the BCM M4 stock. They have one that is " BCM M4 Milspec Stock Kit - (GEN 2) - BLACK - Standard" for 82.95 and one that is "
BCM M4 Stock Kit - (w/ Milspec Rec Ext) - Standard" for 64.95. What is the difference between the two, is one better?

If you look closely at the front, bottom of the stock, just in front of the adjustment lever, the gen 1 have a radius (curved edge), while the gen 2 edges have no radius, just a straight vertical edge.

The gen 2 pretty much looks exactly like M4 stocks from Colt and LMT, while the gen 1 even if they're mil-spec size looks the same as commercial size stocks from Bushmaster, DPMS, RRA, Sabre Defence, etc.