I always use Auto Brakes, the only thing that varies is when I disconnect. I have not flown a 737 for 20 years and fly the 744, but an interesting exercise in the Sim is to reject at V1 using manual brakes and then use AB in RTO. On the 744 manual brakes uses 200 -300 meters more regardless of how hard you stomp them. To be fair, I think you were thinking about the choice for landing only?