I talked to both of them about 6 months ago and DAG had two prices depending if it needed a complete service or just minor stuff. I felt confident that he would advise me appropriately as to what was needed.
Sherry only did a complete service or maybe told me thats what I needed, I forget. I would think that a complete overhall or whatever is needed. Prices about the same. I did talk to Sherry at length and liked her "no nonsense" attitude.
I will have more than one and they have never been service since I have owned them (20+yrs) and will probably use both of them, when the time comes.