I posted something like this before seeing this topic , I am interested in which is most accurate too. Especially when it comes to winds, I am sure it is less turbulent when higher up, which is the opposite of what REX normally outputs into my Sim, this makes me think ASE might be the most accurate as when I'm at a high altitude using ASE the winds are quite low, if I open the rex weather engine they're much much higher than ASE reports.