REX SKY FORCE 3D is more a piece of art than a scientific wonder. It proves the fact that REX are artists, who make the most beautiful and immersive textures for FSX-based flight simulators.
Yes, the software was released with some 'cheap' bugs, but artists are sometimes a little bit scatterbrained, right? :)
Artists sometimes also like to exaggerate. SF is not a fully-featured, state-of-the-art weather solution. It is "just" an amazing texture engine, which fully replaces ASCA on my SSD.
Actually, I think that REX will never make the best weather engine. Why? Because that's a task for scientific brains - an asset of HiFi Simulation Technologies. At the same time, HiFi will never make the best looking textures. We can only hope that these two top developers will understand their strengths and weakness and cooperate, or at least not intentionally make their solutions incompatible.
As it states today, the winning combination for the atmospheric immersion in P3D4 is HiFi Active Sky + REX Sky Force, period.
On the shots above, you can see this combination in work. All the pictures are unedited and without any manual adjustments of weather or intentionally set weather scenarios.