I shoot a 30 30 now, and have shot the 7x30 in the past. The main benefit I could measure is regarding brass stretch. The 7x30 doesn't much, but the 30 30 does a lot.
Both are pretty accurate out of a Super 14, and I wish that I still had the Waters. If you shoot factory loads, IMHO, it's a wash at appropriate pistol distances.
I've shot the 125 Noslers out of the 30 30 for years, and for me, it has been a great bullet. It zips out there pretty fast on top of 748.