Which has the better downrange ballistics at 500 or more yards? I can go either way because the barrel is not yet chambered (or even installed).

Thanks for the reply. I was leaning toward the 300WSM and have been for some time. I bought a 300 RSAUM arbor for my Aimshot laser boresighter on the advice of the salesguy that it would substitute for the 300WSM arbor he didn't have, but the two cartridges are clearly different. Because I have 21-plus bucks in the RSAUM arbor, I decided to ask before I went out and bought one for 300WSM. Anybody want to swap me $20 for the RSAUM one I have? email me at rootbeer@pocketmail.com and we'll get it together. The manual says I can't get messages from hotmail accounts but I got two last week, so give it a shot.

The consideration should be action type the two are too close to call ballistically. The RSAUM works better in Semi-Auto's since it has a slight bit of body taper. The WSM has slightly more case capacity especially if your magazine is a Winchester or Kimber with a 3.1 length. The WSM is more popular and is likely to be around if only 1 survives long term.
So if you want a Semi-Auto or Model 7 choose the RSAUM. For most other actions I think the WSM is a more prudent choice........DJ