Out to 200 yds. on broadside shots, your 243 loaded with 100 gr nosler partitions will kill whitetail deer just as quickly as a 270, 280, 30-06, 7Mag, 308, etc will.

I don't know if they are worth the difference. But if you want a new caliber, I've shot deer with most of those above, and the 308 is my favorite (just my 2 cents)

Look at a big bore caliber (44 Mag, 45 Colt, 45-70, etc.) perhaps for a little variance and a lot of fun.