gen 1: regular illumination and decent glass quality ($1100ish on a big sale)
gen 2: RDB (red dot bright) illumination and better glass quality ($1200-$1300 on a big sale)
I'd recommend the gen 2 (RDB) if you can get it on sale (some people would even argue it's a buy at $1750 msrp). C_does and brass facts both have videos on this scope.