2013-14 Romo was a different player than before. Romo always had good physical ability, and was always a smart guy. But somewhere around 2013 the game slowed down to Matrix bullet time for him and he started playing at an MVP caliber level.
Early on, the poor-man's-Favre comparisons were fair. Romo was a physically tough, mobile gunslinger who could be baited into trouble. But 2014 Romo married that Favre-ian playmaking with some ludicrous pocket passing efficiency. He simply played a lot smarter structured football than Favre did. It sucks that his body failed him right as he reached the apex of his skill... 3-5 more years of 2014 level Romo would have us looking at his legacy very differently. If he stayed healthy into his late 30s, it's possible that Romo could have ended up with an MVP and a Super Bowl to his name.
Favre was a monster physical talent at QB, and was as pure of a gamer as you will ever see. His fatal flaw IMO is that he wasn't very smart and never had a good sense of risk vs reward. Romo eventually learned how to balance that aggression. Favre's killer NFCCG INT with the Vikings shows how he never did.