Some say that Just flights scenery is the most accurate and smoother running than Horizon's. Horizons scenery could be a little too sharp and the colours are too vivid, but on the other hand the colours are more realistic than just flights, plus you cannot land on water with Horizons scenery as you can with Just flights, and it doesn't run as smooth. I think the night time views isn't supported yet either.
I would appreciate to know what other FSX users own, and what made them decide to buy the particular one.
Steve


