Some things to consider....
Sisterlocks are more expensive. They are a lot smaller, so you can style them in more ways. Sisterlock Consultants must be certified. That includes a training program and a internship type deal, too, IIRC. Sisterlocks are created by using a tool that is similar to a crochet hook. Instead of naturally locking, the hook is used to make a series of slip knots. This means you don't go through the process/journey of locking... you get instant locks.
Because Dr. JoAnne Cornwell patented Sisterlocks, only a certified consultant is legally allowed to do Sisterlocks. Depending on where you live, you may or may not, find a Sister lock Consultant nearby, or you might not have as many choices as you would if you chose palm rolled locks.