[asid61]

I think it really depends on your budget, both time and money.
In terms of time, working with new designers is CAD takes a lot of time. If you don't start designing early, it will take longer to design than to simply do. If you don't own a mill, why design things accurate to 0.001"?

I do highly recommend learning CAD purely for figuring out linkages and geometry, however. That's something easier done on a computer than by hand. I would avoid paper simply because it's more hassle for students than CAD in my experience. 973's RAMP has some good videos on it.

All that being said, your robots already look incredible! I think for the build quality that you're at right now, CAD could really help you get things more cleaned up, but it's not necessary. More important than CAD and design is good strategy.

If you do go the CAD route, a small mill will help you machine parts that are very accurate, so you can get more utility out of CAD.