As I understand it the smaller primer is supposed to be more accurate and it is proven in benchrest shooting, but you would probably have to be shooting full blown benchrest to really see it. In a hunting or general shooting rifle I guess yeah, get them if you absolutely feel like you have to attain every possible advantage....just don't expect any significant returns. If small rifle primers were magnificent then they would make brass for everything.
I had an extremely very accurate 6.8spc once upon a time and brass was easily available with either primer. I couldn't tell by group size in that rifle which primers I was shooting. I suspect you will probably see the same thing in a 260. That said, the PPC and the Remington BR line of cartridges all use small primers to the best of my knowledge and they are known for accuracy.
I think I read where the smaller flash hole is supposed to make ignition more consistent and admittedly things can improve considerably when you correct ignition problems. That said, I wouldn't look for small primers to correct things like poor, inconsistent striker hits, the striker spring binding in the bolt, etc.
I am in the Alex Wheeler school of thought that it all starts with ignition and that proper consistent ignition is always a positive thing. One of the biggest reasons guys like to buy expensive aftermarket brass is the fact that, for the most part, it has good consistent sized flash holes. I personally shoot a lot of Lake City brass and it is not bad, but my biggest complaint and the reason I would probably not try to compete with it is the sometimes very poor quality of the flash holes. Many are way over sized and if I sort my brass for flash hole size and consistency I end up not using more than half.