It's hard to compare because Luck was thrown in the deep end in terms of a complex passing offense, just like Manning was. In fact Arians said Luck was doing things with the offense that Manning didn't do his rookie year. And Manning threw 28 INT his rookie year.
It's not a surprise, often times rookie QB's who succeed have a top shelf RB and defense. Roethlisberger, Sanchez, Dalton, etc. Russell Wilson had the #1 defense in the league, and a top 3 rushing attack. RGIII didn't have the defense though... but they were the #1 rushing attack in the league. The Colts were in the 20's in both rushing and defense. I would guess there's never been a rookie QB post a winning record, let alone make the playoffs, with a rushing attack and defense ranked that poorly.