I have used both, I really like both,I use the 250 Deep Curl or Gold Dot [same bullet name change] for deer and have an exit hole every time so far. I use the 300 when I get a chance to go for elk or bigger game, which is what I believe it is designed for.
My belief is that I want to expend most of the energy stored in the bullet by the velocity in the animal as it does not help anything to waste it in the hill side. There for I try to use a bullet that has just enough energy to exit regularly.