Is there any significant difference between the two pistols?

The 97s has a chrome bolt carrier and the obvious lower rail.  We bought 2 of the 21s, I am happy with mine although I need to figure out how to mount a laser without blocking my scope.   My family member however, is unhappy and converting his into a 97s for the chrome bolt and lower rail so he can mount his equipment on it.   Laser and Light in addition to his already mounted scope.  We did not know there was a 97s when we purchased them.  I still would have purchased the same weapon, while he would have got the 97s.  Our  21s are flawless and I honestly do NOT like the look of that lower rail on the 97s, but that Chrome Bolt kicks arse.  That is the only differences I know of.