[asid61]

If you've only got a simple mill and lathe, it's difficult to make a "modern" swerve drive (that's low weight and size, or comparable to a WCD in both). Butterfly is alright, but I like octacanum more because you can keep things in only 4 modules where with butterfly/H-drive you need center wheel to strafe as well. The strafe wheel will also inevitably have less pushing/acceleration power than one in a swerve drive.

Apart from the balance issues, 3-wheel swerve is nice because you can run 3CIM + 3 miniCIM. However, at that point you are using up 6 motors for drive + 3 for turning, leaving only 7 for all manipulators. For many teams, that's ok, but for some motor-heavy users you might want 8 (2 for shooter, 2 for angler, 1 for intake, 2 for angling that, 1+ for climber?). I prefer using a 4-wheel swerve with 1 CIM each to leave you with 8 motors.

I would say that swerve is equal to or has an advantage over H-drives/butterfly/octocanum in most aspects unless you're 33 in 2014 and are ok with being pushed sideways/drifting when you move. The main disadvantage is losing more motors and taking a lot of manufacturing time and weight. For those reasons I would go octocanum in most situations if you really want the strafing.

On a side note, I think the biggest advantage that swerve or other holonomic drivetrains have over a traditional WCD is being easier to drive. If you start somebody off on a field-centric drivetrain, they'll have no problems getting the hang of it quickly. There can also be a space-saving aspect depending on your overall robot design and the game in question, but more often than not it's negligible.