Some amazing transformations can happen in eyes open conversational work such as with NLP (neuro-linguistic programming). NLP illicit a light to mild trance state and can create deep long lasting changes by working with they way you process information.
In the dental office I have used light to medium trance which take 1-3 minutes to induce to assist in surgeries and even have dental patients undergo root canals without anesthesia injections. If you ask them they say they may have felt pressure but no pain.
Deep trance can sometimes inhibit the clients ability to talk quickly and respond the way I sometimes need them to during regression when communication is important. However, sometimes it's best to encourage deep trance when transformational dreaming is the goal.
That's the long answer. Powerful change can happen equally effective in any level of trance.