The .45-70 with a "Marlin load" will kick a LOT harder than a .308. BUT, only the Garret and Buffalo Bore factory ammo are loaded that hot. Most factory ammo is actually quite mild.
I'll be honest, the kid talking about "405grn bullet over 70grns of powder" gave away the fact that he doesn't know jack. Don't bring wikipedia specs for the original black powder recipe to the table and pretend it means anything.
Frankly, the .45-70 and the .308, even with the same recoil energy, will TYPICALLY feel as if the .308 recoils more, for the simple fact that it is faster. What's known as "recoil impulse" is what comes into play. If I push on a car slowly and roll it 3ft, it hurts me much less than if I run into the car running as fast as I can, causing it to roll the same 3ft. Impulse, or the time required to transfer the energy, is what makes the difference.
My wife runs a Marlin 1895 Guide Gun with Hornady Leverevolution 325grn FTX's pushing 1792fps average. I borrowed her rifle last year to drop a 160 class 11pt at 250yrds, which is plenty far for most hunters. She's 5'3" and 125lbs, her soundbyte is that this load/rifle combo "recoils like butter"... Man up, factory loaded .45-70's are NOT bad on recoil...
That's not to say that the .308ME isn't a great round, nor is the .308win, but if I were wanting a .308, I'd get a .308win in a bolt gun or BLR (but I HATE the BLR). The .308ME isn't going to have the staying power, so you're going to be stuck sucking eggs in the not too distant future with a rifle you can't get ammo or brass for (unless you want to stockpile brass now, which is only available from about 3 sources, or start cutting it from .307win brass, which is also only available from about 2 sources).
The .45-70 isn't going anywhere. The .308ME isn't going to last. That's my determining factor here.