depends on what else you have.
If you want ONE rifle (aside from say an AR-15 or other very specialty gun)
Then I'd say go for the 30-30 due to
1. more available ammo
2. less recoil
3. slightly flatter trajectory
if #3 isn't a big concern, I'd even suggest looking at a levergun in 44 magnum. (this will take elk off the table, but then, I think 30-30 for elk really limits you to really close ranges, and not a ton of elk are taken really close)
If you already have a second hunting rifle, something in say 308, or 30-06, or 270, or any of the common big magnums, then you can rely on that gun if ammo scarcity becomes an issue, or you want something less flat, etc.
In the case where you already have a good standard hunting rifle, and are looking for a fast handling brush gun, then I say go for the 45-70, it has all the fast handle, and twice the Wham!