I believe both of those are franchises. That means an owner pays for the name, has to meet some standards, and for the most part, how they have thier gym is up to them.
It is best to visit an individual gym versus going by a name. I've worked out at several different Powerhouses, and they all have a different feel.
Visit during the hours you would like to train. Observe the staff, the facilities and the crowd. It is probally not free, but you can get a trial workout or membership. If you do this, ask the owner (not just the counter help) if you can have your trial membership fee credit towards a membership if you sign up.