I would think that the 25/06 Rem. is for all practical purposes a 6mm/06 when it comes to performance. I am not a fan of the SM's and would not even consider an SSM's. I had a 300 WSM and it cycled poorly. I am guessing because of the shoulder angle. But , hey, I am old .... and stay with what works. Hard to beat the 30 cal. cartridges that have been around for decades .... 30/30 Win., 30.06 Spr. , 308 Win., 300 Win. Mag.