PRP for hairloss, which delivery system gets better results - injecting PRP or using a dermastamp with PRP?

I want to try PRP for hairloss. Female aged 33. I have talked to different clinics and some use injection to put PRP into scalp and others use Dermastamp. Which is more effective? What questions should I ask when enquiring about PRP and what is best amount of treatments and time in between? One clinic does 6 treatment package spaced 1 month apart and another does 3 treatment package space 3 months apart.