As the title says, how much do you explain about why you're leaving a practice, if you're unhappy with it?

In my situation, we go to the same small facility for both PT and OT, and the OT is just honestly useless, so I'm going to stop going (have only had an eval, and 2 sessions). I'm not sure whether to say that they're not able to do the major things that I'm looking for help in (ie feeding), or that the person seems disorganized, and as though she's never worked with infants before, or just something vague like "it's not working out." Given that I really like the PT I don't want the office to think I'm some snob or something.. WWYD?