Adder, it's very relative...faster you fly with greater pitch you'll cover more angels per second! Logical isn't it?
However best and most recommended way of climbing to ceiling is pitching for 0.9M. You'll notice that you'll have to reduce pitch as you climb to maintain 0.9M. Air density is lesser up there! Full AB throughout the climb!
But if you wanna climb from say 5.000m to 8.000m in least time, firewall your throttle gain some speed and pitch up 90°. You'll probably overshoot but you'll climb as hell!