The DA shells aren't really slugs; they're what many handloaders refer to as "round balls". They aren't seen very often so not many people know what to call them. They are also sometimes called "pumpkin balls" depending on who you ask.
A round ball that is properly sized to the specific shotguns bore (since all barrels vary a little) can be somewhat accurate but most of the reports I've read/viewed on the DA ones are 5-6" groups at 10-20 yards. If you're just looking for blasting ammo and don't really need to hit your target with the first shot, they'll do you just fine. If you are looking for a slug that can actually hit something, you're better off looking for cheap foster slugs (the hollow base kind). Consistent 4-5" groups at 50yds with just a bead sight isn't too hard to achieve with even cheap foster slugs.
I often think of round balls as like shooting really big buckshot, one at a time. After a few you'll start to see how your gun patterns (not really a "group").
If you're going to be going through a lot of slugs, add another vote for reloading. I can load 1oz Lee slugs for $.25/each if I have free lead but even paying for lead, it only brings it to around $.40/round. A used Lee Load All 2 for $40-50, a cheap melting pot for $30-40, and a mold for $30 and it wont take long to break even and start saving money. Shotgun powders are starting to become available more frequently if you look around enough as well.