[Chris is me]

2791 used the 6" Vex mecanums last year and they worked flawlessly all season. Even after getting a tether tangled up in them, or tipping and falling onto them, they didn't break. The true roundness of the wheel really helps make driving smooth.

With a really good gyro and some code, you can really make these work smoothly. I would recommend follower wheels if you are attempting accurate autonomous path planning.

Now, when is mecanum a good idea? I wouldn't do it in most cases; 2015 was an exception as it made landfill stacking significantly faster and the field had many tight corners. Plus obviously the lack of defense.