have both, but can't compare apples to oranges...
1st off, I almost only exclusively handload, but I do have both a 7-30 Waters barrel (14") & a 6.8 SPC barrel (21")... also have a 10" 30-30 barrel that is accurate enough for deer out to 150 yards
personally I think the SPC has the most "potential" but since you don't handload, I think you'd have to check factory ammo available... a quick check, & I didn't find too many "real" hunting specific 6.8 ( that is actually in stock... I checked Midway )... maybe you can find it loaded with a good hunting bullet, looks like there are quite a few made... so, that would be my 1st choice, provided you can get a good hunting bullet... otherwise I really do like the 7-30 Waters... I've never used it on game, but most all factory ammo is going to be loaded for hunting game...