Hostility

I did a google search to try to find the most info on this. But figured id ask. I have 2011 f150, 5.0, 3.55 gears. Stock 18" chrome rims and tires. Now my plan was 33" duratracs for winter on stock rims, then Fuel 18's come spring. But i stumbled upon someone selling 20" rockstars with 33" trail grapplers with roughly 5000kms on them. price of duratracs $1600 installed (roughly). price of rockstars with tires $2200. (cdn prices). Now what would these rims be like in the winter? i ask as my stock rubber is crap in the snow and that was my reason for tires. any input?

Hostility

Also what should I expect with decrease in fuel mileage and power? I'm looking at getting 5 star performance tune in the future to help out also