Patrick, it's understandable that you want to know which service is better, but both seem to be getting a thumbs-up. Unless someone was really displeased by the service of one shop and went to the other for similar work, it's unlikely that anyone will have comparative info on two service departments. Why not just talk to them about price and timing and try to get a feel for how they work? Both Mid-State and Zack's have good reputations.
And I definitely concur with Elias- fix the one you have before buying another. I had one that was so non-functional that I assumed it would take a complete rebuild. A cleaning fixed it up.