I have had warranty's with several different companies over the past 10 years (including American Home Sheild), and they all have wonderful features. When making a puchase , I have several things I consider. First, compare coverage to see which one offers the most (most importantly roof leaks). Then, look at the upgrade options and costs of those. It's will suit you best to choose one with the most covered with the least amount of upgrading. I currently have HSA on my house, and have been very happy with it. My last house had First American and they had very few service reps in our area. I had a massive breakdown of my air conditioner and it took almost 2 months to fix. But, I still got a brand new 13 seer Train air conditioner for a $45 service call fee and of course my renewal cost of $359. All in all, a very good deal.
It's imporant to know how many service providers they have in the area. Your Realtor can probably tell you which companies are the best locally.