Cutler is nowhere near as accurate as Aaron.
His mechanics are not as sound, and are based on raw ability(ala old number 4)than actual fundamentals.
Aaron is fundamentally sound, throws w/pinpoint accuracy, and his motion is quick/compact.
Jay's motion is all over the place. He does get the ball out quick just on his ability. When his physical skills erode, his velocity will erode faster than Aarons' because he depends so much on his muscle than technique.
Aaron throws just as hard a ball as Jay does. That ball to Greg Jennings in the end zone was as hard as you can throw it. I compare Aaron's hardest ball to Michael Vick's ball. They throw lasers. Cutler can throw lasers too, but I think his ball can flutter.
They are not comparable quarterbacks. Aaron's way more efficient and has the same rocket arm. Jay's more gunslinger and more wild. They are apples/oranges.
If you want to compare apples to apples...
Aaron is a bigger, stronger, faster, younger version of Drew Brees. Jay is somewhere between Brett and Jeff George. He probably will end up RIGHT in the middle.