Autobrake should be selected always to enable the aircraft to stop on the available runway. In wet or slippery conditions setting '2' is the minimum as per Mr. Boeing.
Get the speed under control in a comfortable way, much easier with autobrake and less worrying for the punters if the heavy foot of the captain needs correcting inputs.
A steady and smooth deceleration reduces also the uneven wear and tear, beside all this, several checks with heat-sensing cameras provided by the fire service at my home base showed a much lower heat being generated compared to manual braking.
Just my 2 Dirhams .......