[Joseph Smith]

I have experience with two different drivetrain styles. #1 is closed frame 6WD/8WD similar to last year's kitbot drivetrain. #2 is West Coast Drive.

#1. Closed frame (8WD) using 1" x 1" x .125" square aluminum tubing. This is the style my team used in 2011 and 2012. We cut and welded the drivetrain frame together before anything else. This method uses dead axles with all six/eight wheels driven by chain from the gearbox.
PROS: very simple design
Low maintenence
Proven and reliable
Robust
Flexible Design

CONS: Medium to heavy weight depending on wheels
All wheels are chained- no direct drive, so it's possible to throw a chain and lose control of one side
Takes up more space
More difficult to swap wheels/tread

#2: Standard West Coast Drive. We used this style in 2013 by necessity in order to package our wide intake under the bumper. We liked it so much that we decided to use it this year as well. It's 1" x 2" x .125" aluminum tubing, riveted together with Vex VersaGussets with a Vex 3-CIM ballshifter. The center wheels are directly driven and the outside wheels are chained.
PROS: Simple to design
Direct Driven center wheels
Easy maintenance
Fast swap wheels/tread
Lightweight design
Robust Design
Widest possible wheelbase
Less space consumed

CONS: Bearings on cantilevered axles need to be well supported and aligned, though the VexPro VersaBlocks are awesome for this.
Requires more machining capability

I love the WCD and don't see any reason not to use it, due to it's low weight and super easy maintenance as well as the benefit of a maximum width wheelbase and direct driven wheels.