Few things I am observing.
1) Chain use: To put this matter to rest: run your stress analysis numbers! You need to calculate the tension on each chain (both sides of the sprocket). Then use your fancy Machinery's Handbook (Every team should have a copy. Awesome resource
) and calculate the stress in the chain and compare that to the breaking strength of the chain. Remember to include a factor of safety!
2)For Rookies:
For flat game (no climbing) the simplest and most efficient drive train that you can build is two powered wheels that are center aligned (or slightly off center depending on how you want for turning characteristics) with "skid wheels" such as hard plastic caster wheels that don't turn. I've seen more rookies (and veterans) be competitive with this than any other because its simple and effective.
For a climbing game the simplest and most efficient drive train for a rookie would be the six wheel drive platform. It allows you to climb and still have good maneuverability.
3)For veterans:
Build what you can afford. Build what you feel best matches the game. Don't build until you have done your research. If you have resources to build a crab/swerve go for it. If you need to climb something and can afford the treads build a tank. Every type of drive has its pro's and con's so you need to weigh your options and do your research.
4)
Don't get closed off to one type of design whether you've built it or not. The good teams become good because they take a risk and try; they learn from their risks. Many teams have had success at things you may have failed with. Use it as a learning opportunity and to add another design into you book of tricks. Every year everyone comes out of the season saying what they could have done this or that better. Well don't forget it, and do it better
.