No doubt Cupp has had an amazing year, but his career has been injury plagued up until this point. Still though, he had like 1100 yards in only 14 games a couple years ago so he's been on the brink of breaking out for awhile.
And as far as Stafford goes, he's always been an elite talent and there's no denying that. He was the #1 pick for a reason. And Dak's arm made him a conditional 4th round pick, again for a reason. That being said I realize that over his 6 year career all of Dak's stats were accumulated in garbage time while Stafford's were amassed in a career full of nothing but clutch play, but Stafford's accuracy has netted him a career mark of (63%) on 7.3 yards/attempt which is 3+ percentage points below that of Dak's career mark (66.6%) on 7.6 yards/attempt. Now I realize that one can still reasonably come to conclusion that Stafford is better than Dak, but given that their career marks are well within range of each other (although Dak comes in ahead of him in many if not most of the categories) it's a bit ridiculous to claim that anyone who disagrees with this assertion has their head in the sand or that Stafford's being better "isn't even debatable".