Per Chuck Hawks tables the .243 Win shooting a 100gr bullet has a Maximum Point Blank Range of 283 yards vs. a .25-06 shooting a 120gr bullet has a MPBR of 291 yards. Recoil velocity on the .243 shooting the 100gr bullet is a 9 vs. a 10 shootingthe 120gron the .25-06. Not much of a difference there. A 100gr bullet is going to be plenty for varmits and I think you can get a little heavier bullet if needed as a backup for deer on the .243.

Not much help. I just thought I would look at the tables and see if there was much difference.