I own MANY Elite scopes, in the 4200 and 3200 series. The 4200 is noticeably better and worth the extra money.
Of the Elite 4200s, I own several of the following: 2.5x-10x-40mm, 4x-16x-40mmAO, and 4x-16x-50mmAO.
On a long range rifle like a .300WM (which I also own a few) I would go with the 4x-16x. Now, if you don't mind the extra weight, then I would get the 50mm version. I have a 4x-16x-40mm mounted on a .25-06, and a 4x-16x-50mm mounted on a 7mm ULTRA mag.
Zachary