[Aire valley]

For what it's worth, in my experience ,over many years, far more people race indoors, during the winter months , than race outdoors during the summer months.! I don't know why, but it always seems the case.
Therefore, just concentrate on a great indoor facility and don't consider it as just a practice area for outdoor racing.
So, although a fully carpeted area is good and gives massive grip, in my view, the most enjoyable, and satisfying to drive, is a multi surface area, combining, grippy, carpet, sections and slippy, wood or indoor tile, sections.
Although a dirt track "appears" to be popular, it can be quite high maintenance and difficult to get right, as well as being less popular due to being dirty and different cars /set up required.
So, go for multi surface..!