For me, it's either WCD or KOP. Either can be purchased and put together with nominal amounts of machining and programming work.
Presuming you use all-COTS for either drive train, these are IMO, of course:
- WCD is easier to customize around an overall robot design since the frame consists of only 5-6 basic parts.
- WCD maximizes robot stability by putting the wheels at the outer-most maximum dimensions
- WCD makes it far easier to experiment with and find the right wheels - and then maintain them throughout the season
- WCD makes dealing with chains super-easy. If a chain snaps (literally) because of a wonky new offseason defense (@Nate @Matt ....
) then a fix requires just a few parts of adjustment rather than removal of anything.
- WCD reduces flexibility when it comes to bumpers. There are ways to design bumper mounts to make them secure, and most of them over-complicate the frame design when compared to the simplicity of WCD itself.
- WCD can be done with rivets, but IMO it is far simpler to design and execute if a team has a welding sponsor. The middle cross rail usually drives me up the wall, unless we have a welding sponsor.
- If welded, WCD frames are less forgiving if not properly cooled. The reliability of chains presumes the side rails are perfectly straight.
- WCD setups have very few COTS "plug-and-play" options that are designed specifically for WCD. Most gearboxes used in FRC will require some sort of custom mount in order to direct-drive one of the wheels in WCD. This isn't an insurmountable issue to fix for an individual team. Yet don't expect to go to the 3 major FRC gearbox suppliers to find anything that adapts non-WCD gearboxes to a WCD setup.