Hi,
The Mike One has a 5mm blade thickness, the Mike Three, 4mm.
Mile One has the hollow screw fasters pivot and butt. The Mike Three, only at the pivot, small diameter blind screw at the butt.
Mike One has the wire pocket clip, the Mike Three has a conventional tab pocket clip attached with the hex nut/glass breaker.
Otherwise very similar, same blade length, OAL.
Both great.