hardcast, while performance on a normal sized hog at 18-20 yards would be around the same between the .44mag and the .500sw, you can bet your bottom dollar the .500 has tons more power and effective range. I know since I have several .44's and a couple .500's. They are like night and day.
I've taken whitetale, hogs, and elk with both in handgun configurations. The old man had a .44mag marlin that I took a couple hogs and 1 whitetail with. It was adequate for both. As was said earlier, there are several other straight walled cartridges that would be better but with your range expectations a light little .44mag marlin would be just fine as long as you stay within it's limitations. Hogs can be and are a very tough animal but they aren't bullet proof. A good old heavy boar will have that cartilage shield built up and that thing does absorb a ton of energy from bullets so I would target them quartering away and trying to hit a bit behind the shoulder. Head shots on broadside boars are fairly easy but don't take those on whitetail. Much smaller target area and much more likely to maim a whitetail. Straight on headshots on hogs can be tricky. Their skull has a very steep slope to it and that can cause a bullet skip rather than penetration. Some are under the false impression that their skulls are really thick and tough but in reality they are far from it. Just that angle can cause problems.