[Solace]

ok, i'll give it a shot

• weight
  as light as possible without sacrificing strength. it depends on the material too. 1/8 aluminum weighs the same as 1/4 inch plywood (i think, correct me if i'm wrong), but you would use more plywood than you would aluminum. however, you can only cut so many holes in a skeletal aluminum frame, while the number of holes you can put in a plywood chassis is usually limited only by one's endurance and the battery of the hand drill.
  
• traction
  you are correct in saying that 4-wheel drive is the easiest way to get reasonable traction - however, there is a tradeoff. the more traction you get, the harder it is to turn, and so the lower your motors must be geared in order to overpower the side traction. this problem can be solved by any number of little tricks (omniwheels, retractable casters or skids), but each of these just adds more complexity and, seeing that they lack mounds of experience, could possibly hinder a rookie team more than help.
  
• turning
  manueverability is, IMHO, the most important quality of a robot. If you can supplement manueverability with lots of speed, then your golden. If you can be everywhere instantly, then you can and will dominate, no matter what the future game turns out to be (remeber 25, anyone?). as always, though its a tradeoff between manueverability, traction, and speed. It is also easy to have way to much manueverability too, though. I would at all costs stay away from permanent casters as a way of boosting manueverability. I know from my time in the scouting service that fixed casters on a robot is a sure sign of inexperience (I have heard of some teams who were pretty good anyways, but i've never personally seen one). Casters make it precision driving difficult, especially at high speeds, and basically cut traction to zero. all an opponent has to do is hit you from the side and your bot will spin like a top. my personal favorite design is the 6 wheel design, with the 2 center wheels lowered just a bit. it basically the traction of a 4 wheel design and gives it loads of extra turning power.
  
• attachment space
  if your chassis has a solid bottom, there is rarely a lack of space for mounting things. plywood works great (you can paint it, you know, and it actually looks kind of cool).
  
• repairability
  everybody disses plywood as a building material, but they really shouldn't. It is extremely forgiving, will flex under imact, quite strong, and extremely easy to handle and repair. despite what naysayers might think, aluminum will bend long before plywood will break, and when aluminum bends it stays bent, while playwood will just spring back into place.
  
• looks
  some people say that its ugly, and it certainly is if you leave it unpainted, but its easy to give a wooden chassis it a coat or two of paint before you start screwing things on to it. (although i didn't personally agree with my teams color scheme of choice this year, i can't tell you how many people asked me what our robot was made of - it was hard to tell that it was wood unless you really got close. look for yourself)

wow, that was a lot more than i intended to write, but i guess what is done is done.