That's interesting. It once was the other way around back in the brick and mortar days. 410 was readily available and 28 was scarce, at least in smaller towns. If 28 is easily obtainable in SD rounds, although pretty similar to 410, 28 does have a bit more powder and possibly capacity for volume of bbs. Bore diameter for a 410 is 0.410 while 28 is 0.545. 410 shells are 3 inch and 28s are 2 3/4.
The two are pretty close but the 28 has slightly more recoil. As a kid, I started with an Iver Johnson 410, but a friend had a Remington 28. I shot both side by side while shooting skeet one day. My 410 had full choke and his 28 was modified. I hit the clay pigeons a lttle better with his gun.