The 260 shooting a 140 gr bullet is going to have considerable more knockdown power than a 243 shooting a 100 gr bullet given the speed is nearly the same. I too just enjoy having rifles in my collection that are different calibers in case I get the itch that day. I enjoy shooting just about everything from 444 marlin to 22 so why not have them all!

Just don't tell the wife hide them in your safe.