For On-Road my choice would be carpet (but not the black US variant). For Off-Road it's more difficult to tell. I've never driven Off-Road indoors. The indoor tracks I've seen photos of, don't really look like Off-Road to me (regardless of the actual surface). I've grown to like driving on Astroturf outdoors, as long as it's not flat like a table and has enough room for big jumps, etc. The small indoor carpet tracks I've seen on most pictures, just look like On-Road tracks with two or three tiny little hops (wouldn't even call these "jumps") added.