mike6161, .410 is admittedly a pretty strange caliber. Remington's slug load is 88 grains at 1830 feet per second, nothing like any other .40 or .41-caliber projectile. Closer to .30 Carbine, actually. The slug loads are hard to evaluate because their accuracy can be uncertain, particularly from a gun with no rear sight.
.410 is common in sports since it is necessary to compete in a certain variety of skeet. Also it makes a pleasant shotgun for small game. Experts can hit waterfowl with it too.
Now, comparing regular .410 to a .45/410 long gun like the NEF is something I know little about. I bet the straight .410s pattern a little better but that is only a hunch.
So, while it's been described as "the .22 rimfire of the shotgun world!" it's the opposite of .22 rimfire in that the market for it is very small, it's harder to train with than a full-sized shotgun (not easier), and the weapons are often unfamiliar and obscure (like a Western Field bolt-action repeater, or a converted Lee-Enfield single-shot, or a Saiga with a Kalashnikov action and a vertical box magazine). Still, it's an interesting chambering and I've lusted after more than a few.