For Christmas I got a pair of 4.00-12 Deestone tri-rib tires. They'll fit both my Speedex and my Cub. Both tractors have more of a street tread currently.
I have real problem steering the Speedex in deep snow, and I use it for some snow removal. It doesn't have steering brakes.
I don't expect to operate the Cub in the snow, and if I do it does have steering brakes which should help.
I'm inclined to put the tri-rib tires on the Speedex, thinking it will help steering in deep snow.