When it comes to textures quality, Active Sky 2012 comes nowhere close to REX textures - REX is a king of texture kingdom. Some of Active Sky 2012 textures are simply broken (but you will probably not notice it, if you do not compare them to other textures). As a weather engine, I've had no experience with nex REX engine, the old was bad, and the Active Sky engine is very good (only waiting for patch with fixes...), so I also would gladly hear whats the comparison of those engines.
I'm most interested in REXE fog/haze/visibility generation - no problems with this? Does it finally do a good job with it? Or are there such bugs like with Active Sky, where you start with low visibility, great fog/haze, and when you fly to 4000/5000 all the fog/haze dissapears suddenly?