I put the 4-16X40 on my 300RUM.

3 x 9. I have 3x10's and rarely crank it to 10 other than on the bench and sight in. In the field I usually have it set between 5-7 depending on the spot.

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its impossible to tell you what would be best unless you give us a usual shot distance...maybe its 75yds..then id say a 3x9 is fine...maybe its 300 then the choice is yours but the 4.5x14 would be nicer...all depends..if you have trouble shooting with a 3x9 because the range is a bit far move up a bit...

still the question persistes, are you hunting the clear cuts or powerlines?? when i back home in tomahawk for deer seasons my 300 mag. supports a 2x7 cuase i am in the hemlock swamps. also removing the simmons 44 mag 3x9 on the '06 for the same reason and going to a straight 4x...i know that not what you want to hear, get a the 3x9 nicest you can afford optics. the light gathering and picture will better...i was always curious on the red led scopes.

If you are hunting in open country go for it. You will get a lot of use out of the 14x. I have a 6 x 18 on my open country rifle and use the 18x a lot.
If you will be hunting in the timber you may wish you had something that went down to 2x or 3x. On my timber rifle I have a 2 x 8 and it is normally used at 2x.
IMO 2 by 10 or 3 x 12 is an ideal compromise.
These days scopes are getting so expensive it is getting more important to choose the "right" one the first time.