243 is quite a bit flatter than 6.5 out to 500 or more yards with similar heavy or light for caliber bullets. 6.5 hits a bit harder and recoils more but for deer sized game, I think the 243 is a better hunting cartridge out to about 300. For smaller game, I’d stretch that to 500.
Most of these shifts in popularity aren’t grounded in ballistic realities. If you target shoot past 500, that’s a different story. I own rifles in both calibers
I've mentioned this before.
Despite the advent of high BC bullets, laser range finders and ballistic software on our phones, the older high speed cartridges still have their place for hunting.
The average shot on game is still under 300yds. Flatter shooting cartridges still help when we don't have time to lase things and our wind reading might not be exact. A lot of the high BC bullets don't even begin to show their advantage until way past the average shot on game is taken anyway. I remember reading articles years ago about spitzer bullets VS round nose. Most of he conclusions at that time were close to the same. At the average game shot distance.. not a lot of difference.
Still.. IF tag sales are correct and the number of hunters is dwindling, then getting a TGT rifle in a TGT caliber that subs as a deer rifle makes a whole lot of sense.