Depends on your build and budget. The best coat will be the one that looks the best on you and certain brands fit different ways. Ariat, Tailored Sportsman, and Grand Prix make some excellent ones but most of them are around $300-400 range. The Elite (which is made by Grand Prix) and RJ Classics make some decent coats that are a little less. I would suggest trying some on and see what looks the best on you.
The best coats are made of a 100% wool or sometimes a wool blend. Some of the cheaper ones are made of polyester. I have an Ariat that I love that is wool but has stretch panels for easier movement.