When I read "7mm" I assumed that you were asking for us to compare the .270 Winchester to the 7mm Mauser or 7x57mm cartridge, not the 7mm RM. If so....
I have both, and wouldn't care to give up either. If I had to, it would be the 7mm that had to go, although I have extensive experience with it in many different rifles. The .270 is more comparable to the .280 Remington, and with slightly better ballistics than the 7x57 *with similar bullet weights and configurations*, is just more versatile. We have a current run of six deer with six shots at ranges from 120 to 260 yards on our medium to large sized Maine whitetails with the .270 and 130 grain bullets. None of them ran more than 20 yards. The 7mm is a fine cartridge but not as accurate with the loads I prefer in MY guns. Still it makes a nice short stalking rifle for high or thick places, while the .270 is really at its best with more barrel length. The Mauser cartridge is a bit easier on the shooter, too, so is a good choice if the shooter is small-framed or young.
Your .270 can also handle bigger stuff than deer, generally better than the 7mm Mauser, although an exceptional shot could take pretty heavy game with the Mauser, with the right loads.
I've owned a lot of rifles, but never could see the sense in the 7mm Magnum. It's a nice flat-shooting heavy hitter, but uses an awful lot of brass and powder to do the job that a .280, 270 or .30-06 could do just as well.
Ammo for the .270 is no problem, lots of different bullets and brands in many weights are available, to cover the full spectrum of shooter's needs.