I'm personally bonded to the 270 Winchester as the best whitetail round. But that's fully acknowledging the subjectivity of this and the reasons people developed other cartridges since the .270 came out (way before that newfangled 243
).
It wasn't what I took my first deer with but it is what the rifle my mom and dad bought me when i was 14 was chambered in (cuz they didn't have any .30-06 chambered savage 111s in the store at the time and we weren't leaving empty handed…best "compromise" ever!) and it's what I've taken the most game with. I know full well it doesn't do anything about 3 dozen other cartridges don't do pretty much the same…that being said I don't know if too much improvement can be made on the original 270 as an all purpose deer cartridge, especially out of a 22 inch barrelled sporter weight rifle that doesn't kick too much for beginning shooters like I was to learn to shoot well with. It really does occupy a ballistic sweet spot to my mind, the boring old 130 soft point at 3000-3200 fps may be very old news at this point but it's deadly as all get out.
I own a 300 Winnie, a 270 and a 243 and must say I really do see a difference moving up the cartridge power levels, especially between the 243 and the 270. I fully acknowledge the 300 as totally unnecessary and possibly ridiculous but I like that rifle and just use it for pretty much everything now and it certainly doesn't waste any more meat than the 243 or .270 in my experience, despite the claims of such by those who have never even shot a .30 caliber magnum of any kind.
Anyways, I would argue the .270 as a much better all situations whitetail round than the .243, and I own and use both. Bearing in mind I live in northern Saskatchewan, so these are significantly bigger bodied, thicker skinned, thicker fur, more "ready for winter" subcutaneous fat kind of deer than the warm-weather Texas whitetails mentioned above.