killswitharrows –
First, given proper bullet selection, any of the three (.444, 450 or .45-70) will do a great job on anything you’re going to hunt in North America.
Second, with 40,000 CUP handloads designed for the Marlin rifles, the .45-70 is the flattest shooting of the bunch. It has a bit more case volume than the 450 and will launch bullets with similar Sectional Density as fast as the .444 and bullets of similar weight faster than the .444. Bullets for the .45-70 range from 250g Barnes X to 500g – and heavier if you include cast bullets.
Third, I would definitely stay away from ported barrels. Not only are they extremely loud, they spit stuff out the ports, which can be both painful and dangerous when it hits bystanders.
After a couple years of looking for a good used Marlin chambered for any of the three cartridges I finally ended up with a .45-70 out of sheer luck – I walked into a gunstore and a two-year old 1895SS was going for $249.94. Needless to say, it became mine very quickly.
Finally, handloading for any of these cartridges is highly recommended. I load 300g Laser Cast bullets over 13.5g HS6 for a very accurate, very mild (about 2/3 that of a .30-30), and very inexpensive load – about $2.60 per 20. These loads are excellent 50-yard loads and will the bullet will consistently penetrate 11 water jugs. My hunting loads get 350g North Fork bullets at 2183fps for about $1 per loaded cartridge. This load has taken a mulie buck at 197 lasered yards and a 6x6 bull elk at 213 lasered yards. I was very impressed with the results in both cases. I practice out to 300 yards and would not hesitate to take a shot at that range if I had a good rest. There are a variety of loads I build that are in-between these loads in terms of cost, any of which make a good hunting load. (I have more loads for my .45-70 than any other cartridge I load for. It’s that much fun.)
My suggestion is to get a Marlin – doesn’t much matter which one as it probably won’t be your last. I started with a Marlin 375 (.375 Win), became addicted and got the .45-70, and now have a .30-30 as well. When I want to have fun, these are the rifles I reach for.