Client; person using services of lawyer or professional person or company

Patient; person receiving or registered to received medical treatment.

If my insurance covers it I prefer patient. It also denotes to me that the person giving the services keeps in mind, my best interest. It also sounds much warmer and personal to me.

Client sounds cold and business like, as if their interest come firsts

I also suspect that client came about as a political correctness term or as a way of justification for HMOs not to pay for MH treatment.

Personally I would prefer my T to think of me as a patient I'm a person with feelings. It also makes the boundaries more clear.