Just remember the 4WD helps get you going but does not necessarily help you stop or take turns. You see enough 4WDs/AWDs in the ditch on various highways. A lot more important for that are the tires. That said, I've rented a Dodge Nitro (liked this for switching between 4WD and RWD on the fly) and Jeep Liberty (AWD only) which were good for the same snow-covered highway (Coquihalla and connector in B.C.). Just have to be very gradual at the wheel - definitely no abrupt turns.

p.s. I got a FWD Dodge Caliber (ug'd to an SUV) a year or two ago in Canada. Performed wheel on the above highway when there were jackknived semis. All rentals from now-closed National locations around YVR.