The win mag will get you another couple hundred fps gain, and that translates to range, more than anything.
Well it translates to a flatter trajectory, I wouldn't say more range. Both the 06 and Win Mag are effective way past what the normal hunter will ever shoot. What the extra 200 fps really does is impart more energy with the bullet at normal hunting ranges. Which in turn usually gets a larger reaction from the animal hit. However, all is moot if you can't shoot the Win Mag as well as the 06.