I believe most carrieres stick by the "all on / all off" philosophy.
The only exception being some operators using the A/T ARM mode as a "sorta-alpha-floor-protection-even-though-it's really-speed-floor-protection" during the manual stages of approach.
Advantage 1 - hit the TOGA button and you have the GA thrust setting available (where you may not get full whack but enables 1500-2500 fpm ROC). If in manual - well, you can't really have an SOP that says anything but "hit the target N1", and especially when light, things start happening very quickly! Flew with an operator with this policy, and out of 3 go-arounds from manual approaches, I had to take over 2 of'em
Advantage 2 - you can bug and fly Vref +5 without extra wind increment (IIRC! - not on the 73 for a year now
), since the A/T is still engaged and will correct any underspeed.
Draw-back - if you float the aircraft and don't have your hand on the throttle, it may start adding N1 to keep target speed as you coast 2 feet above the runway.
Throw your SMS at it and see which comes out top
