A2z looks cleaner, have seen examples of frames with the chasertech style most cause the boss to break. Could just be down to bad setup. It does look cool though.
A2Z needs a hold drilled through drop out to stop it rotating backwards if you absentmindedly hold the brake on and roll slightly backwards - I've torn a brake hose doing that in the past....
Chaser tech is yet another name for a brake adaptor that has been around since god was a boy. Its good as long as your brake boss is firmly welded into place as it puts a fair bit of stress into it under heavy braking. Buggered up a trek of mine in the past snapping the boss clean off.
Better idea would be to brace the brake torque arm against the stay in some manner. All after market brake adaptors need a bit of bodgineering.