I totally agree with Sarah Louise, but another factor to take into account is how comfortable are you with the staff?
The first place I went to seemed to be technically fine, I just got bad vibes; scientific I know

The second place I went I just had a feeling that the staff respected and cared for me. I felt very happy and confident that they were doing the right thing for me. They also gave me a lot of advice on skin care in general, so I did feel I was being looked after rather than just another customer to be zapped.