I also own both, a .243 in a Ruger No.1B and a M77 in .260. There really isn't a dimes worth of difference as far as I'm concerned but if your going to shoot factory stuff for a while, go with the .243. Since I got my No.1, the .260 has stayed in the safe and so far the .243 is 5 for 5 on deer, all one shot kills just below the ear. No tracking required and a breeze to field dress.