If you don't handload, then the easy decision is to simply go with the 6.8 SPC. It offers considerably more options in commercially available ammo, and is a lot easier to find locally. Now, on the other hand, if you plan on reloading, then the choice isn't so simple. Personally, I would go with the 7-30 as it handles the heavier bullets (125-150) a lot better, and offers more case capacity. Brass is certainly cheaper in the 6.8 SPC, but you can resize .30-30 to 7-30 with little effort.