The 260 is a step down in recoil for sure. Lighter bullets always help.
The 243 is a step down even more from the 260 and is plenty capable on deer out to 300 yds.
We've been using the 243 and 6mm Remingtons and 25-06 for big Wyoming muleys and whitetail for many years. Broadside or slightly quartering body shots pass completely through the vast majority of the time, especially when under 200 yds. It's pretty easy to get complete pass throughs at 300 yds with lung/heart shots. My son uses the 85 Barnes, I used to use the 95 and 100 grn Partitions. More recently, Ive used the 100 Barnes in 25-06. A good friend uses the 115 Berger with good results.
I promise, with proper shot placement and good bullets, any of the above mentioned cartridges are plenty good to 300 yds and even beyond on 250-300 lb deer.
Muzzle breaks make a huge difference, but are you willing to put in hearing protection for each and every shot? Even the close shots at 75 yds? I am not. In fact, if I am shooting deer at 75 yds here in Wyoming, it generally means the deer already knows I am there and there is very little time to get the shot off before the deer bolts off, never to be seen again.
I love muzzle breaks when we have the right protection in our ears, but a good friend is still suffereing from ear pain a month and 1/2 after the fact from being next to a different friend that was shooting a muzzle break this past season. I've suffered the same pain in the past from forgetting ear protection with a 357 magnum revolver........my left ear still isn't right a few years later.
Another option is a mercury recoil tube installed in the stock by a gunsmith. It will make the gun heavier, but weight is the best defense against recoil, and the mercury tube is even more effective.