I am a big fan of IRC's Serac XC tires and getting ready to order a pair to replace the studded tires on my winter/backup bike. I've bought 3-4 sets of Seracs in the past couple of years and never paid much attention to the XC-Lites. The main difference appears to be weight (450gr vs. 580 for 2.1's). All other things held equal, I know it's better to have a lighter tires but am not familiar with the trade-offs you make to shave grams. I am not a racer... just ride cross-country and like to use solid, dependable products. If I go with Lites, can anybody tell me if there is a noticable sacrifice I need to take into consideration?