To me personally, I have owned both the 300 RUM and the 300 win mag.... yes the RUM is "better", yes its "faster" and yes its "more powerful", and becase of the mentioned reasons above, I sold it and kept the 300 win mag....
To me it was more of a "pride" thing more than anything else,.... I feel that Im a "skillfully" better hunter if I can hit my target all the way out there past 400 or 500 yards with a 30-06 or 308..... I know the 300 win mag or RUM is a "better tool" but I look at them differently.... I think the a real marksman is someone who does alot of practice with his tool and I see my self practicing a hell of alot more with my 308 or 30-06 than my 300 win mag or RUM....
I typicall go to my local gun range with 60 to 70 rounds of my 30-06, over 150 rounds of my 223, and sometimes 20 rounds of my 338 win mag or 375 h&h and stay all day on sunday from 10 AM all the way till 5 PM..... I shoot most of my ammo then I go home. If I was to use my 300 RUM, I highly doubt I can go through 60 to 70 rounds.... I know its doable, but I didnt wanna go through the hastle, so I sold it.
Now, because I do 90% of my practise at 300 yards, right now, my best ever groups were 4 rounds inside of a bullseye that the diameter measured just a few notches under an inch...... To some that may not seem alot but, I used to get 3 to 4" groups @ 300 yards a year ago, now Im doing MUCH better and I owe it all to long hours of practice