I've owned and shot both...for whatever reason, in similar rifles, there is a noticeable step up in recoil from the 7 Rem Mag to the 300 Win. I currently have a SS 700 in 300 Win that I had plans to make my one and only big game rifle. I just can't get used to the recoil to shoot it well. I take it with me on every range trip and shoot at least 20 rounds each time, but accuracy is still suffering. If I can't get the hang of it, I'll probably rebarrel to 7 Rem Mag or 270 Wby. I've also considered having a brake installed, but I really prefer not to have one on a hunting rifle.
That being said, I think the 300 Win is a much more versatile cartridge. In my neck of the woods, you see at least 10 7 Mags for each 300, but it's mainly open country/beanfield hunting where a 7 Mag/140gr combo is fantastic. In my opinion, a 300/165gr combo is great for open country, while 200gr partition/accubond is perfect for elk
