Here is some information that I gathered that you might find useful.
I have a 20in bbl rifle chambered in 30-30, and an 18.5 in bbl rifle chambered in 308.
Here were my results using a chronogragh.
Note: Both were fired on the same day and under the same conditions.
Note: 30-30 = Win 170gr Power Point.
308 = Win 150gr Power Point.
Note: I ran both of the cartridge's average velocities thru my ballistics program, along with the E.C., elevation above sea level, etc...... and here is what it came to.
Velocity and K.E. at 20ft from the muzzle:
30-30: 2199fps with 1825ft/lbs of energy
308 : 2769fps with 2553ft/lbs of energy
200yards:
30-30: 1602fps with 969ft/lbs of energy
308: 2194fps with 1603ft/lbs of energy
I have hunted with both of these rifles, ( Deer, as well as hogs)....... and while the 308 has quite a bit more behind it's bullet at the 200yard mark compared to the 30-30, both are very capable at killing.
Especially if the shot from either rifle is placed in the same spot (Sake of argument.)
Both seem to produce similar wound channels at 200yards or closer, and typically exit the animal. (Quartering shots included)
The difference really showed itself to me when the distance is increased, and if I'm hunting something bigger than white tail deer.....but that wasn't your question.
BTW..... I did shoot a few boxes of 147gr 7.62x51mm on the same day, and under the same conditions. (Win "white box" Q3130)........using the same 18.5in bbl rifle.
It's really gonna come down to the rifle, and what you prefer to shoot, unless your wanting to hunt bigger critters like elk at 200yards, or whitetail deer at distances over 200yards.