Any recommendations for either?

I have used alpine inspections, http://www.alpineinspections.com/, twice for purchases in the last 3 years. One was desoto and one dallas by Joe Pool lake so I'm sure Arlington wont be out of the way.

I just used Ross Heating and air, https://www.rossheatingandair.com/, and was very pleased with price and thoroughness. I didn't have any work done just a service and inspection as it was an older unit. This was in Dallas and he's based in mansfield so will probably work for you as well.

Good luck!