The lego one definitely was cooler, sadly lego just wouldnt stay together well enough, or remain accurate enough to do the job.. at least not the lego I had, and I wasn't prepared to glue it.
In the end, the commercial unit used only 1 motor, compared to the 3 I had in the Lego one.. but it could use precisely folded sheet steel where I had technics beams ;p and the force the commercial motor can deliver (has a huge gearbox hooked to it) is really quite something.
On the plus side, sitting in the middle of the lounge floor building the lego one, surrounded by an ocean of sharp pointy lego bricks.. brought back a lot of memories ;p (Wheres the little block thing gone I had a mo ago.. It was right here.. ah.. I'm sitting on it.. again.. )