Why is it better to start of with a featherweight than a heavyweight...

pro's:

Less costly to start out with and learn. A basic mobile platform can be achieved by cannibalising 2 screwdrivers (12v or 18v), 2 esc's capable of handling 30amps, 1 LiPo battery and a transmitter, receiver. Screwdrivers comes with build in gearing and can be hacked easily to attach a wheel straight onto it. You're looking at about 200 pounds in total costs

Easier to handle. 13.6kgs can easily be picked up and set aside whereas a heavy will suck up space. Plus should a more experienced roboteer live nearby it becomes far easier to bring the machine to have him have a look at it.

Components like batteries, esc's and motors are more readily available.

Just as many events to use them throughout the year. (perhaps more)