All things being equal I still feel that velocity (of both the round and the corresponding recoil impulse) is a major factor in how things feel. Ive shot both the rounds mentioned a bunch. A whole bunch. But the 308 mostly in 168s and 180s. FWIW I think the 12 ga has more kick but feels less sharp than the 308 wit a bit less recoil but a bit quicker or sharper.

This can explain the fact that the worst recoiling gun to my body is a 378 Wtby. Its way worse than any 458/460 wtby etc..... Its just so dang fast............

FWIW Don't be scared of the 308 or even 30-06 if you shoot the 12 ga. If you shoot that 12 ga, IMHO you won't even be bothered by a 7 rem mag.

Jeff