I didn't sacks aren't important, but that's not the only indicator. Pressures force sacks and they force bad passes. Hardy had six sacks and Lawrence 8, and four games Hardy didn't play. Lawrence had a whopping 1 sack going into 10 games of the season. So two made sacks on the season out of way over 700 snaps a season...
Further, Hardy saw way more double-coverage than Lawrence and Marinelli had him playing the tackle position a lot more by the end of the season. You can say he has a few better games by the end of the season, that doesn't mean he was the better DL, or he would have done as well without Hardy on the field. Teams aren't scared of Lawrence.
The Cowboys defense was trash without Hardy in the field and their first four games was their worst performance and Romo was in the field for two games.