I wonder if the "2.0 crossover" track is actually the series 4 144 (Polaris does like to stretch their track lengths: run it banjo tight and it's a 146). If it is the series 4, which has a 2.52 pitch, and they're using 9t drivers, it would explain why they'd use QD2 there, but not on the 2.6 (assuming they're using the typical 7t 2.86 pitch drivers). The bigger driver would make a significant difference in rolling resistance, an advantage to the 2.0. Having rode quite a bit on a 144x2, I can say it'll handle some decent snow. If you want to be able to run full speed down the trails and losing some deep snow ability isn't a big deal, go for it. If keeping up with 155+ sleds in deeper stuff is a priority, then the extra lug would be a good idea.
With regard to cooling, it should be fine – the 146 Slash sleds have a bigger cooler because they're more likely to be used as crossovers. If you did have issues, a bigger snow flap would probably take care of it.