If you are already set up for 45 caliber then I would get the 45 Colt, if for the 44 then the 44 Mag. If you reload, it does not make much difference if you are not set up already. Remember the 45 Colt takes .452" bullets and 45 cal rifles .458" bullets so there is no exchange between those of any kind, not even the primer. If you are going to buy your ammo, no question get the 44 Mag. While heavy 45 Colts are available to buy, they are mighty pricey; even more pricey than 44 mags which are not cheap. As far as reaming one out, I personally do not see the point. Get a 444 Marlin or 45-70 Gov barrel to start with. Again 454 ammo is pricey as is 445. The 445 is not widely available unless you reload. Unless you want the different factor, I would not consider those options. Unless you hand load I would not consider those options either. As far as knock down power for hunting either one (45 or 44) will get the job done, with in their limits which are similar. Fun factor, either one. I guess I did not help a whole lot, it really comes down to which one you want the most. I gave you some things to consider. Good Luck and Good Shooting