Vanderbilt actually finished the season better than Florida did in terms of the SEC standings, as the Commodores wound up 19-13 and 9-9 in conference play, but based on nERD, they aren't as good.
Vandy's nERD (9.22) ranks them as the fourth-best team without 20 wins this year despite their above average offense (84th percentile) and defense (64th percentile).
Vanderbilt's biggest issue wasn't their schedule (the 92nd-toughest) but rather its own consistency. According to the math, Vanderbilt was just the 288th-most consistent team out of 351 schools. Vanderbilt suffered a seven-game skid in the middle of the season, all against SEC opponents.