Typically when you quick tap LB you will bring out the last piece of equipment you were holding without having to open the radial. This works all the way until a player opens a book or quest map and from that point tapping LB opens the quest map/book first no matter what equipment is selected, even if selected after reading the quest book. Switching the equipment to come out first no matter what would give the game a much smoother feel. In many situations you have to remember if you have a quest active or not so you know if you have to tap LB once or twice to access your equipment.
