I picked my CDC as she was really motivated and inspired me loads, easy to talk to and understanding. Go with who makes you feel comfortable, not embarrased.
Ask them about what services they provide .... ie what happens when you come to see them.
How often they work - especially if you need a special time or day. (some CDC's are part time/some work only evenings/some don't do weekends etc).
Do they keep a full stock in all the ranges.
Then see how you feel you get on with each one - your relationship with your CDC is important in keeping you on the straight and narrow at times when otherwise you'd waiver.