Five really big advantages of SA wheelguns patterned after the 1873 Colt SAA:
1) Accuracy. The cylinder is fixed in place. Each time you swing the cylinder closed on a DA wheelgun, you're forming a new alignment between the cylinder and barrel. In an SAA-type design, that alignment is locked in place. If it's set right, it doesn't get unset.
2) Toughness. Fewer moving parts. If you're bringing one handgun along on a deep back-country trip, an SA wheelgun is least likely to fail you of any repeating handgun. NOTE: the one downside of the SAA pattern is that the base pin (the "axle" that the cylinder spins on) can come loose, esp. with serious calibers under stout recoil such as the 44Mag or above. A stronger cross-latch spring or an aftermarket base pin with a locking set-screw head is recommeded for a serious-duty SA. Both fixes are user-installable and less than $30 for the most expensive fix, more like $5 or less for a stronger latch spring.
3) Ergonomics. The SAA was designed by people who worked with hand tools daily, as opposed to computer workstations doing industrial design today. The SAA feels
so damned good in the hand if you know what you're doing with it. It can also handle big recoil better than any other, assuming the fit of the gun is proper for the user.
4) Because of those ergonomics and the fewer-parts thing, an SAA-pattern can be lighter than a comparable DA wheelgun for the same horsepower level. A 39oz 44Mag SA will be more comfortable to shoot one-handed than the same weight DA wheelgun shooting 44Mag.
5) VERY fast "first strike speed". Done right, drawing and firing an SAA-type is damned fast, even without getting into "fanning" techniques that tear the gun up. You draw while cocking it, and use the cocking stroke to help pull the gun clear of the leather.
The downside is the reload speed sucks. I'm working on improving that
. So far I've got mine to gas-eject the empty shells as I shoot. I have a magazine feeding system in the design phase, waiting only on some cash I have coming from a lawsuit to do a custom cylinder in 9mm. At that point my total rate of fire should match or perhaps slightly beat a DA wheelgun
.