Hardcore single shot fan here. Whether it's field target or silhouettes (both on timers) or prairie dogs, heck, even pest birds at the dairy (hundreds of shots in a couple hours), I will ALWAYS choose single shot. And do.
The only use I can rationalize for magazines would be a speed event like at EBR/RMAC.
Problem with magazines is that they need loaded. One of the reason I went away from magazines in air guns is that I was spending more time loading mags then I was spending shooting.
Grew up with a single shot H&R break action Handi Rifle in .223. Make the first shot count.