Here are some stats from the 2014 to 2018 NCAA first rounds.

Straight up wins and losses for round 1.

1 seeds are 19-1
2 seeds are 19-1
3 seeds are 16-4
4 seeds are 17-3
5 seeds are 14-6
6 seeds are 8-12 (3 lower seeds favored)
7 seeds are 14-6 (5 lower seeds favored)
8 seeds are 12-8 (9 lower seeds favored)

Based on past results, the 6 seed is the single worst place to be if you are in the top half of seeding. And that is probably due to the fact that the 9 and 10 seeds are mostly from the P5+Big East bubble teams while the 11 seeds have a lot more of the A-10, M.Valley, West Coast type bubble teams.