A standard capacity AR15 carries 30 rounds. It's the "colloquial evil black rifle" that epitomizes everything wrong with firearms, in the eyes of anti-gun folks.
Compare to a standard capacity handgun, we'll use a standard size Glock 9mm; holds 17 rounds standard.
Compare to a reduced capacity handgun (restricted to hold 10 rounds.)
I can fire, accurately, 3 rounds per second from a 5.56 "Assault Rifle", or handgun (standard capacity or extended capacity).
It takes me 10 seconds to fire all 30 rounds out of the AR15. It takes me 4 seconds to load the rifle. (More complex than handgun, magazines are larger, more steps required.) Another 10 seconds to fire another 30 rounds out of the AR15. Benchmark = 24 seconds for 60 rounds.
Now take the standard 17-round capacity Glock. I have to reload the Glock 4 times, but it's faster (takes under a second if you're proficient, less complicated.) So we'll factor one second for reloads. It still takes me 24 seconds to fire 60 rounds. (Same as the AR-15, matching our benchmark).
Now take the reduced capcity 10 round handgun. I have to reload this SIX times to fire 60 shots - for a total of 26 seconds (60/3=20, +6 for reloads), to fire the same 60 shots.
I can still shoot a reduced capacity (restricted) handgun 60 times in under a half of a minute.
Where's the benefit here?