I will temper this comment by saying that I live in CA and (for better or worse) we can only use lead free bullets for hunting here.
Using this as my starting point, then the availability of improved BC bullets for your .260 is MUCH better compared to the .223, in fact nearly double the BC for common twists.
As an example, looking through the GS Custom web site for options, firing a .223 at high MV is nearly useless beyond 100 yards compared to just light loading the .260 for 200 - 400 fps slower and using higher BC bullets.
A friend of mine has a .223 and the negligible recoil and light weight ammo is attractive (and the rifles are cool) but I can't logically justify buying one compared to just using low recoil rounds in my .270 win and concentrating my money into making that rifle and my shooting skills better.
Not that a person needs a logical reason to own a second rifle, but I nearly bought another rifle this year simply to have a better chance of obtaining ammo to take my son to the range.