Id take Gronk over Witten in a heartbeat
I wouldn't. I'm happy with Witten. I don't think people (Cowboy fans, media) truly appreciate how special a player like Witten is. First off we have no idea if Gronk and Romo would have good chemistry, as the poster Mrtxstar stated. Secondly year in and year out for for the 11 seasons people have been trying to downplay how good Witten is. Witten is always being compared to other TE's in the game. I'm tired of hearing about If Witten was only as good as Jimmy Graham, or Gronk, Gonzalez, Antonio Gates. My argument is, Witten has very quietly put together a HOF career on some very bad offensive teams. How good would Gronk be if he had a combination of Quincy carter, Chad Hutchison and Drew Bledsoe throwing to him his first 4 seasons?
Here's some numbers: (Pro-Football reference.com mobile) - source info
Jason Witten: 191 games,10502 yards, 943 rec, 57 tds
Gronk: 66 games, 4473 yards, 313 rec, 57 tds
Gonzalez: 270 games, 15127 yards, 1325 rec, 111 tds (Man how AWESOME was this guy?)
Gates: 179 games, 10014 yards, 788 rec, 99 tds
Graham: 78 games, 4752 yards, 386 rec, 51 tds
Shannon Sharpe: 204 games, 10060 yards, 815 rec, 62 tds
Ozzie Newsome: 198 games, 7980 yards, 662 rec, 47 tds
Kellen Winslow, 109 games, 6741 yards, 541 rec, 45 tds
Jay Novacek: 158 games, 4630 yards, 422 rec, 30 tds
Witten stacks up with the best tight ends. I am impressed after looking that up that Gronk has as many TD's that he does. But the stat that pops out in my mind is the duration of Witten's career, the consistency, and the fact that he has never been in a system that features the tight end. I also want to mention that stats do not cover the X factors of leadership qualities, playing hurt, telling Randle to shut up when he was talking about Dez, living through the Terrell Owens experience, etc
So here's my summation. If I had one play to win the super bowl with and I had to pick either Gronk or Witten to beat a safety and score I would pick Gronk. If I had to pick either Gronk or Witten to be a centerpiece of my franchise for the next decade I would take Witten, no hesitation.