I've heard the opposite from an instructor in BC - "if he fan stops we're going for the trees - people do strange things in cold water when their brains stop working, like trying to swim into the back of the plane".
Well... I've not done a study on this, but I've read several accident investigation reports where aircraft have crashed into trees and it is not encouraging reading.
Especially not with spruce or pine forests. First you smash into a stiff trunk one metre (3 ft) in diameter, then you fall 30 m (100 ft) to the ground. I would prefer ditching in a nearby lake or river any day.
Hypotermia is a real survival risk, of course, but it doesn't set in so quickly that it would affect your egress from the aircraft.