I know it's not popular for some reason, but I think a locker is better for ANY condition. If I know the back end is locked, I know if I haul balls into a corner it will break loose. The key word here is know. The most important thing for any driver is to know exactly what their vehicle is going to do. The reason I could keep up with all my V-8 Heep buddies in my Sammy, on logging roads, was because with the rear locked up I could pitch it sideways on every corner. Granted I should be dead 20 times over for doing with less than 4psi in the tires sometimes, but I'm still here. As long as you know how your vehicle acts with the locker on ice you'll be fine. Most of us have 100hp at the most, so I don't think we can get to crazy. I'd always want the extra traction for take off, especially on ice and snow. Or, coming out of a corner sideways. Maybe I just miss desert racing. My 2 cents.
Brian