If you look back (search) you'll find quite a few discussions on the wide body (235) vs narrow body (200 or 190) and how we've found wider to be better - mostly stability around corners, the ability to carry speed through corners, partly because of being wider, but partly because of wider bodies enable more DF.
Also - on foam tires vs. rubber - rubber just don't cut it. they aren't soft enough to allow the tires to grip with so little weight. Tell you what, though, you bring your rubber tires, we'll bring our foamies. . .and we'll bring an extra set for you too!
They do cone and they do wear out. But I've found that I go through more foam tires on my NTC-3 than I do on my 10L2 - and the L2 is "wearing" roughly 25shore tires and the Nitro is wearing 40's (roughly) - so the softer tire is wearing better than the harder nitro tire.
But, we've discussed this one too!
As to 6 cell vs. 4 cell - 4 cell today is prolly as fast as 6 cell was a decade ago. However, 6 cell is far faster than that.
6 cell is always going to be faster than 4 cell if, for no other reason than that the voltage is 50% higher on 6 cell. Roughly - each cell is ~1.5v. (makes mult easier) - 4 cell is 6v. 6 cell is 9v. Which is going to turn the motor faster? Higher voltage. (yeah, it's a generalization but is generally true)
Plus, you'll have longer run times since you've also increased the total amperage capacity.