Avery certification harder than 3M? Not to hate on any brand or anyone but 3M certification was 10 times harder. Avery was easy as hell. Besides the double layer cuts what was mentioned there was no challenge for an experienced installer.
3M, on the other hand, had the old sprinter door which has the deep channel with double wall and also the HHR front bumper. If you never done them before you won't be able to do it. Especially the HHR bumper.
Beside that avery is all about vehicle wraps. 3M had wall wraps, cinder blocks, bricks, floor install, corrugated panel with rivets with no air release vinyl. That last one alone was harder than the whole avery certifications.