If you do decide to log it in some form or another, I wouldn't log more than a few hours unless you are planning on learning the systems in depth. You never know when someone in an interview will open to that page and say "Ah, I see you have time in a King Air, I used to fly that too, describe the unique characteristics of the landing gear system". (Or something to that effect) A few hours will go overlooked, but if you have pages of time in this plane, Murphy's Law states that you will get systems questions during an interview.

Following that same thought - if you are only going to get a few hours in it and you aren't sure if you can log it, don't log it. You are allowed to just have a flight for the fun of it, and to gain some good experience without logging it. Nothing says you have to log the flight. Although most pilots will log anything they can even vaguely justify. Just remember that whatever you put in that log book you might have to justify to someone else later. And you better hope they agree with your thinking.