Reciprocal turnbacks can be a killer. Turning back to a cross runway is generally more achievable. Practice turnbacks are good training but its in the context of a canned scenario, with everything going according to plan and with forewarning. A real engine failure will never be like that. Having said that practicing a turnback once every six months in the aircraft is, in my opinion, setting yourself up for a scare or worse so I'm strongly of the mind that practice turnbacks belong in the simulator only. If you must practice turnbacks in the aircraft then it must be properly supervised and documented. Even then the scope for someone to go off script is precipitously high.