Speaking for 1991, we went from having a VERY surprisingly rigid bot in 2014 that we couldn't find out how it wasn't breaking, and in 2015 we heavily stepped up our material use, design process, and manufacturing techniques. That 2014 bot was mostly 8020 and the kit chassis.
The 2015 bot used mostly aluminum tubing. Luckily, a parent stepped up to teach welding, and I think everyone on the team was grateful. And the swerve drive, although based on our 2012 design, was neat.
tl;dr: Robot quality was heavily improved between 2014 and 2015.
May as well add that our outreach is fairly huge now, watch out for more awards