I did rank Smith #4 on the team, BTW, so I'm not a hater. That penalty was a serious mental mistake that lost a football game.
Romo's passing ability is far more significant than his mobility and it's what allows him to make everyone around him better.
In 2011 with Doug Free at LT the Cowboys had 327 first downs, 6008 total yards, 38 TDs, and 34 sacks allowed. In 2013 with Tyron Smith at LT they had 325 first downs, 5458 total yards, 45 TDs, and 34 sacks allowed.
The running game produced 7 more TDs than we had in 2011, some of that is Murray's health, and some of that is Smith, but looking at the big picture it's a drop in the bucket next to Romo's passing/threat of passing.
Smith is good, but he's no 2007 Flozell Adams.