Well, I'm going to suggest you look seriously at the .260Rem.
I've had both. The .243's are gone, and the .260 is definitely a keeper.
Just yesterday morning, I took out my .260 for the first time.
Not only was I favorably impressed with the performance, the rifle is "lucky" too.
I had been sitting in my favorite hunting spot at the airport where I keep my plane, and am allowed to "thin the deer head" to reduce a/c-deer collisions. (retired game warden and active flight instructor put me in a favorable position).
I'd been sitting for ~45min. The county had parked their tractors/bush-hogs overnight and weren't finished with last grass cutting. About 8:15am, they cranked up the tractors and proceeded to start cutting the far side of the runway. I decided to pick up my folding chair and move into an adjacent cut-over area. I had stopped momentarily at the edge of the woods and looked across the runway to see which way the tractors were heading. At that time, an 160lb 8pt buck (weighed) started galloping across the runway headed straight towards me! I dropped the chair, swung the rifle on him and watched him through the scope. About the time he crossed the near taxiway about 60yds in front of me I fired the first shot. I didn't lead enough and hit him behind the rib-cage and knocked him down. He jumped up and kept heading towards me, to my right. Second shot took him through the mid-rib area, but at the time I thought I'd missed. As he reached the edge of the wood line, he hesitated and I shot a third time and took him through the shoulder just under the spine. This shot blew a mist out the far side and dropped him where he stood.
The first shot hit the edge of the inside of the pelvis (hip bone) and was lodged just under the hide on the cheek of the rump. (Speer 120gr Hot-Core at 2,850fps; 47.0gr of RL22). The second and third shots completely penetrated and were not retrieveable.
Recovered bullet weighs 77.4grs and looks like a "hot-core" advertisement. Perfect mushroom. Wound tracks were narrower than with a 7mm-.30cal but about what I expected given that the 6.5's are intended to exhibit superior penetration as they are likely to be used on larger game and through such as the .264Win mag.
I've had numerous bullet failures and lost deer with the .243. I don't currently own one, and don't anticipate ever owning another. For varmint and even deer for that matter, I find the .22's such as the .22-250 perform better for me than the .243. Just my experience.......
In retrospect, the .260 dosen't perform (at least with the 120gr Speer) noticebly different than my .257Roberts or .257wby at longer distances. But, the absolutely delightful little Remington Mod7 is a real keeper.... I shoot left handed, but I can't even remember working the bolt x2.... Or even having to re-aquire a sight picture. Almost like I was shooting a semi-auto... But then, I've been hunting with b/a rifles for over 40yrs.....
The next deer will likely fall to a Hornady 129gr Interlok, just to see how it performs.... Then, later this season I'm scheduled to go on an east Texas deer/pig hunt.... There, I'll try some 139 and 140gr bullets.....
However, based on an example of one, I'll give the decided advantage to the 7mm08. It makes the deer flinch a bit more with a similar hit.... And with a 150gr bullet, the bullet I recovered would have exited the deer..... The friend I'm going to Texas with, used my 7mm08 in '05 to take a very large 6x6 bull elk in Colorado.... 3 of 4rds he hit the elk with likewise completely penetrated the chest broadside, with Nosler 140gr Partitions, and a single 140gr Sierra Pro-Hunter busted both shoulders and lodged under the hide. It too exhibited textbook expansion and weighed ~98.0gr expanded.
So, I'd be inclined to pair your .243 with a 7mm08. For practical purposes, I can't tell the difference between the 7mm08 and the .30/06......
But, if you're looking at a particular .260 I'd be tempted (I was, and bit.... and not sorry I did).