Hay rb: I'm not so sold on the Cor-Bon ammo for a number of reasons. One is the amount of hype they put into somewhat lower powered loads. If the best Cor-Bon will get you for a 300 grain 444 is 2150 feet per sec., then Mr. Peter Pi should go read a couple of reloading manuals before he hypes any more of his stuff. Right off hand I think, the Hornaday manual lists a couple of different loads in the 444 300 grain weight to 2300'/sec.
Beartooth Bullets also lists a whole buncha loads just like that. Also, Garrett and Buffalo Bore produce some whoppin' business end smackers for the 444. While you might get more calculated muzzle energy from a fatter bullet at the same velocity than you would from a narrower bore, that narrower bore will penetrate a heck of a lot more than the fatter one will. What I do know is that the 444, in 300 grain weight, from a Contender pistol, has taken the African big 5. That's enough for me thank you. And, not to whizz all over your single shot, but my lever can put out anywhere from 4 to 8 300 grain hard cast slugs at 2300'/sec, or better, while you got only one Rugerism.
Truth is that it is neither fair or accurate to compare a modern cartridge with one about 130 years old. With the older one, these days, you have the unnecessary move to heavier powder charges and faster velocities when it is simply not needed. Worse, it is dangerous for those with guns that should shoot only the original loadings.
One thing remains true - both work. The preference for caliber is yours. Getting slightly more muzzle energy from one single shot doesn't top what you can put out from a similar calibered lever. And I have always thought it a dangerous proposition to rely solely on caliber than on capability (yours). It's sort of like the young Police Officer who depends on his mace/club/gun rather than his training and skills. By the time you get it out of your holster you have already been run over.
Of course, if your most dangerous game is a point scale on a target frame this entire discussion becomes moot and I will simply close with my wishes that you thoroughly enjoy your new toy. Mikey.