RE: 243 vs 30-30
The 243win, 260rem,and 7mm-08 are great and the latter would be better for deer and hogs.
How ever the 30-30win and 35 rem would be my pick for say 150 yards and less. And at say 15-75 yards shots they excell and neither have much recoil.
Next the new Marlin are great and only getting better. My choice is a 336 in 35rem, I shot a 200lb bore at 30 yrds and it drop right there never took another step. The 35 offer better performance than the 30-30but either will work fine. Mine is a 336D 35ren with a leupold VXII 1-4x20mm from 10 to 200 yards it rocks. The HornadyLeverevolution ammo works great but plain old rem core lokts in either work fine.
I hunted with a 6mm rem and after say 5 yrs replaced it with a 270win mainly do tothe larger caliber bullets just do work better at dipatching game. That was 30 yrs ago I pick up few more guns since then but love the 35rem and 358win for most of my hunting done under 200 yrds. These 336marlins sure handle great get one you will love it. Its my go to gun for under 100 thick stuff.