The Swift has suffered a number of setbacks in its lifetime. Bad press early on, due to people loading 38 gr bullets at 4100 fps. When you add in the powders they had back then, it was hard on barrels. In 1963, Winchester dropped it as a chambering and replaced it with the 225 Winchester, another semi-rimmed cartridge (based on the 219 Zipper Improved) that was a little milder. Meanwhile, ammo makers quit making ammo and brass for the round, the last US manufacturer was Federal, and they dropped the round back in 1980. So if you wanted a Swift, you had to shoot Norma brass. At the same time, the 22-250 had been introduced as a factory round, and the rest is history.
Back in the mid-1970s, I used to shoot with a bunch of guys who had all kinds of varmint rifles, but the one to beat was always the 220 Swift. It was a Ruger 77 Varmint, and it would shoot 3/4" at 100 yds (I know, doesn't sound very impressive, but at that time that was pretty darn good for any rifle). Another guy had a Ruger 77 Varmint in 22-250, and it shot real good, too. Those two used to go back and forthe about which was better. So they decided to determine which round was better. They loaded 100 rounds of the same bullets, primers, powders, and hired a chronograph (at that time, that was a costly proposition, as the screens cost $1 each and were good for one shot). The upshot of the whole thing was that the Swift threw a 40 gr bullet 130 fps faster than the 22-250 (less with the 50-55 gr), but it had a 2" longer barrel, so they attributed it to that. Other than that, no major differences. So much for the 220 Swift mystique.
The 220 Swift is a neat round, and when loaded reasonably is no harder on barrels than a 22-250. Problem with that is there are lots of guys who look into the case and see there's still room for more powder and just can't resist.