I generally fall into the big slow bullet camp. I think you will find that in the 30-30 the heavier 150 and 170 bullets hold their velocity and energy better farther downrange than do the 130's. Does that equal deader deer? I doubt it. It does mean that a shot that strikes on the edge of the kill zone will have a better chance of penetrating where it will count, at least according to the conventional wisdom.
I do have as example of the extreems though.....
Last year I shot a spike at about 25 yards with a Hornady 180 XTP in my 357 Maximum. Muzzle velocity was 2060 fps. The shot was for practical purposes broadside. The shot struch and broke the front leg just below the shoulder, drove through the heart, exited leaving a 1.5" wound and exited the far ribs, breaking two and left a caliber size hole on exit. Deer dropped like it had been hit with a sledgehammer and was dead when I got to it.
Two weeks ago I shot a spike at 25 yards with a 405 grian bullet from my 45-70 at a muzzle velocity of 1200 fps. The shot was quarting toward (a return trip to the location makes me lean toward not quite broadside) The bullet struk the foreleg just below the shoulder, breaking the bones, yet deflected and exited below the neck (bullet turned at least 90 degrees) Deer went 15 yards and lay down but was alert and watching me as I approached, he simply couldn't run. Obviously I did the coup de grace thing.
The XTP performed above my expectation while the pure lead bullet was equally surprising in a different way (I do not think it failed, it brought the animal to a stop allowing a clean dispatch) A light fast bullet vs a slow heavy bullet.
My conclusion is both approachs are valid, the question being is the right bullet being applied for the task. I don't think a pure lead bullet at 2060 fps (or above for that matter) would have performed as well as it's slow cousin did, and I think a harder bullet at the slower velocity woud have plowed right through and dropped the deer with all the effect of the XTP on last years deer. Chose a bullet that is right for the caliber, the velocity and the game, and know that even then there will be surprises.
That 45-70 load is a perfect example of the right bullet in the right place and still strange things can happen. That load is atypical of the 45-70 and is for practical purposes the standard which deer cartridges and bullets were judged for 50 years, and a few still consider it the standard.
The 357 Max load is a ballistic twin of the 30-30 170 grain load and is the modern standard against which all the rest are judged. Confused yet? :wink: