Just looking at pure energy, the .30/30 will deliver between 1,300 ft lbs. and 2,000 ft. lbs at the muzzle in various factory loads and will keep a good portion of this at 100 yards. The .44 Rem. Mag. will deliver between 600 and 1,100 ft pounds at the muzzle, with lots of altitude and power loss down range. Out of a carbine with hot hand loads, I wouldn't be surprised if you could get a .44 mag to match the low-end .30/30 performance, at least at close range. And it will make a bigger hole.
On the other hand, I suspect you'll get better expansion with the faster and smaller .30/30 bullets, making up for its initially smaller size. The .44's main advantage, as I see it it, is its shorter length and consequently greater capacity. It may also be a little easier to work the lever. I have a .45 Colt carbine and an old .30/30 Marlin. The Marlin is more accurate, but I can deliver a lot more bullets a lot faster with the Winchester, and it's plenty accurate enough. Those 255 grain slugs make a nice "smack" sound, too ;-)