They serve two different purpose -- the quick access only disconnects you from the Wi-Fi network / Bluetooth devices (all except Apple services / devices) and the settings toggle stops the radios whatsoever.
I'll again say it's not intuitive at all and it's not communicated well (if at all), but for us here that go the extra mile to research, having two separate such options is handy.
Yeah: press Home button, tap Settings, tap Wi-Fi, tap the toggle.
A lot of digging indeed.
Like, come on.