This is one item we don't cut corners on. Get the best you can afford and take good care of it. There is nothing worse, this side of Purgatory, than being wet and 30 minutes from the boat ramp in 40 degree weather. The cheap, plastic specials get brittle in cold weather and simply break apart. When you really need it, a good rain suit is worth every penny it cost.
Safety is a prime consideration anytime, but is doubly so in cold weather.
Winter is the time to wear it like it was a religion. If you do find yourself in the cold arms of Davy Jones' locker, you may need to get those boots off in a hurry and cutting the laces may be the fastest way. Additionally, anglers have been known to become entangled in monofilament line while falling out of a boat. Think that one over. Well, I think I'll go throw another log on the fire and hope the river thaws by next month.