Every comparison I have seen between the 7.62X39 to the .30-30 was more about trajectory than terminal ballistics. The trajectory of both is nearly identical out to 200 yards, and lackluster at best (compared to other .308 caliber options), but the .30-30 shoots heavier bullets as fast or faster.
The .30-30 is clearly superior on target (on edit: hits harder), but both are adequate to 100 yards or so, a little farther for the .30-30.
The answer to the OP remains, use the rifle that you shoot best. If you can put them all on a pie plate with the AK, but not the Mosin, use the AK. If you shoot both the same, I would use the Mosin.