I've owned both, and where I hunt, 200 yards is getting to be a long shot, so the '06 would be my choice, here. Now, if you were to be consistently shooting beyond 300, and more towards the 400 yard type shot, I would think hard about the .300 WinMag. With a 165 grain bullet, it has a wicked flat trajectory (but for deer, so does a 25-06), and where I would really consider it is if I needed to use heavier bullets.
A 300 WinMag with 200 grainers is a potent rifle for bigger game than deer, and the heavier bullets is where the big 30s will really shine.
If Elk (as you originally mentioned) were on the table, at longer range, I would have to vote .300 WinMag.
