Think outside the bun
Hey guys, the two cartridges are different. Way different. Just because they both can throw a bullet between .308 to .310 diameter about 2400 fps does not mean they are the same.
Having killed over 50 eastern whitetail deer with the .30-30 let me say it is a great [eastern whitetail] deer cartridge.
Having seven grandkids that graduated from shooting BB guns, and .22s to shooting my CZ 527 in 7.62x39mm, let me say the "Little Russian" is a great shooting cartridge.
Sure, the .30-30 has more power. But, it costs more to shoot it. A 20 round box of .30-30 ammo is somewhere between $12 and $15. A box of shells for the Little Russian is $4.50. Those grandkids can sure burn up the ammo so while I have both rifles, I haul out the 7.62x39 when the kids show up along with a 500 round box of Silver Bear hollow points.
Sure, handloading helps but .30-30 cases suck green tomatoes. After 4 or 5 loads they get ready to break their heads off. You can reload the Little Russian cases until the primers won't stay in. But, hey, it's cheaper to buy the Russian ammo than it is to reload Boxer primed brass.
A good .30-30 lever carbine can shoot around 2" groups at 100 yards with issue sights, but most are 4" guns with factory stuff. My buddies AK is good for 4"s. My Little Russian [CZ 527 bolt gun] with its 2.5x8 Leupold scope is good for 1" with hand loads and about 1.5" with the cheap Russian ammo. All are adaquate for hunting, but the better sights and trigger on the Little Russian make it a winner when we are shooting targets. [Did I mention the ammo is cheaper?]
So, if you are choosing between the two for hunting, choose the .30-30. If you are choosing one to be fun to shoot, choose the 7.62x39.
Both are "better" for their chosen purpose.