Marlin, I think, has dropped offering the porting on factory guns. It does make it louder, and I wouldn't want to be the guy shooting at the bench next to you.
If you want to port, I would suggest the longer barrel.
If recoil is a concern, you may want to look at better recoil pads. IMHO, the 45-70 does not kick all that bad, as it's more of a push than a punch.