I've driven quite a bit on the BFG KOs and found them to offer pretty decent winter performance, even at temperatures well below freezing. Mind you, that was on a 6,500 lb van, not a 4,000 lb Xterra.
We also had some vans running on Blizzaks, and there was no question that the Blizzaks were superior. Not a huge difference, though. Either of those tires offered an enormous improvement in winter performance over the OE Bridgestone all-seasons.
For our Xterra, though, there really wasn't any question as to whether we would go with dedicated winter tires. As that annoying old oatmeal flogger used to say: it's just the right thing to do.
As for size, we went with 31x10.50R15, which is pretty much the biggest that will fit on the Xterra without lifting it. Even then, you have to trim the mudflaps a little bit to stop the tires from rubbing at full lock. IMO, though, there's no real reason to go bigger than stock. The only reason we went bigger was because we got a great deal on them.
Lastly, I'd be very wary of any tire advice received from XOC (
especially winter tire advice). Some of it is just plain bad, but most of it seems to be based on the experience of hard-core off-roaders who live and play in sunny, desert environments. A lot of these folks figure that since they once managed to drive through 6 inches of snow on the stock all-seasons, winter tires are a waste of money. Others are only concerned with plowing through a foot of fresh snow on their favourite trail. Neither situation has much to do with getting around safely on cold, icy, snowy roads, day in and day out, for six months of the year.
