I haven't found much differance in brands I've got oakleys, scotts, & smiths they each have different models (pick one that fits nicely in your helmet) the important thing is "thermol lens's"(dual pain), & "vented lens's". Smith sells a pair that comes with "quick straps" already on that saves ya $10 or $15. Then to complete the job a "no fog" mask is a must! not only for keepin your face protected against wind burn on the fast trails, but to keep the heavy breathing of the tight trail & powder runs from going up & in the lower vents & getting on the outside of the lens.
With this set up I've never, yes I said never, fogged up!
since you are "sweater" look for lenses that have the most vents across the top.
PS DON'T WUSS OUT BECAUSE OF THE MONEY, BUY A "GOOD" QUALITY HELMET, there's alot of crap out there in mx helmets
"better to bye a good helmet & never need it then not getting one & needing it"