[efoote868]

Speaking from experience of 3 years of robots that used Mecanum wheels (and observing 1 year with swerve).

Mecanum wheels are the most forgiving holonomic drive. If all else fails, slap some skyway wheels on your robot and drive like you were never able to strafe. You can't say the same for kiwi, and you'll be pretty heavily invested in swerve.

Swerve drives have many more points of failure than mecanum wheels. If this is your first season with a non traditional drive train, mecanum will be the easiest to adjust to. Swerve drives have that nasty part where you have to turn your wheels before you go in the direction you want to go, which is another control challenge (having said all that, mad props to the guys on 111 for making it look easy every year).

As far as what you need for a mecanum wheel setup, at the bare minimum get a gyro and learn how to use it. Also learn about trigonometry and the math behind field centric drive.

Design your mecanum drive with either a bit of flex in the frame, or spring loaded wheels. It is very important that each wheel touches the ground, and the carpet at FIRST events typically is not perfectly level.

Last but not least. Buy your mecanum wheels now, along with four sets of gearboxes. Make a drive train with a wood frame and start playing around with it. Don't modify the wheels or the gearboxes, and you'll be able to use them once the next season starts. You'll then have learned valuable things about mecanum wheels that we may have missed here.

Good luck!