RG3 has better statistics in categories such as Quarterback rating (QBR), completion percentage, and touchdown to interception ratio. But Washington is currently running a hybrid West Coast / spread-option offense that limits risk in the passing game. This system is possible because they have one the best rushing attacks in the league. They utilize the same zone blocking scheme that Mike Shanahan used to great effect while head coach in Denver. Washington has the fifth most rushing attempts per game in the NFL. Alfred Morris, the Redskins primary ball carrier, has 1225 yards this season and currently ranks fifth in the NFL. Of course, the presence of a strong running game is valuable to a quarterback because it does two things. One, it makes play action passes much more effective. Two, it limits the number of third and long passing down situations. Good for Griffin because his conversion percentage on third and long passing downs ranks as second worst in the league, better only than Blaine Gabbert for quarterbacks with a qualifying number of attempts. Griffin has less responsibility in this offensive scheme than he would in a more pass reliant offense. His backup, another rookie Kirk Cousins, ran the offense just as effectively in week 15 against the Browns, as Griffin has at any point this season. Griffin benefits from the system he is in.
The Colts threw Andrew Luck into the deep end of the pool and rather than sink, he has had an exceptional season. Luck doesn't have the benefit of strong running game. The Colts have a patchwork offensive line and currently rank 22nd in rushing with many of the teams most crucial runs coming from Luck in the form of scrambles when the pocket breaks down on passing plays. ESPN ranks Luck as the most valuable running quarterback in the NFL. No quarterback has rushed for more first downs, many of them coming on third down. The offensive scheme installed by Bruce Arians stretches the field vertically while providing Luck with few check down options on passing routes. The average distance Luck's passes travel on completions is 8.6 yards, tops in the league. Luck has already thrown for 3800 yards, 7th in the league. Andrew Luck's 3rd down conversion rate is second best in the league. Many of these conversions occurring in 3rd and long situations, which is an incredibly valuable statistic because 3rd down is the most important down in football. This illuminates a characteristic that Colts have already seen numerous time this season, Luck seems to be at his best when the stakes are high.
The Colts have put a lot of responsibility onto the shoulders of Andrew Luck. While he has not had nearly as impressive a year statistically as Griffin, Luck is so much better than traditional statistics indicate. His contributions have turned the Colts from what appeared to be an expansion quality roster into a playoff team because he has led the Colts to victory in so many close games. This makes him the Rookie of the Year, so far.