Dirt for sure
Go against the carpet/astro grain!
It's what the cars are made for

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..!

I would go for New astro turf without sand infill and wooden features on a profiled surface. Everyone's going EOS carpet. Personally I'd rather race on astro ready for the outdoor season.

I think it's safe to say that whatever you decide upon, some people won't be happy with it, others will be......

Whatever you end up using, just do it the best you can. At the end of the day, every track is different. Sand filled astro is not the same from one track to another. It's similar,....but not the same.

Indoors is a bit easier, due to not having to deal with weather changing the surface.

Personally, I would steer clear of anything that is going to give you more work to do.

Dirt - Lots of maintenance (Just look at the USA tracks and what they have to do to keep the surface consistent throughout a race meeting)
Sandy Astro - Outdoors, fine. Indoors, you'll just end up with loads of sand to clear up.

New Astro/Carpet - Virtually maintenance free, lots of grip and no one complaining about dirty cars or sand in their diff :)

My only suggestion is that you cover the jumps with the same surface. Whatever that surface is, keep it consistent. Wooden faced jumps are a nightmare IF you aren't a totally consistent driver.

Good post dude :)

Steer clear of sand...clean Astro surely if you're indoors?

Re features, if you cover them then do them in a different colour, makes a massive difference to spotting take off etc especially on quick sections.