I had used Reflex XTR before and have recently bought Phoenix.

They appear to be very similar although I do believe Reflex was better in a couple of areas and Phoenix better in others.

The Low wing Trainer in Phoenix has some funny characteristics, not sure if its 100% accurate.

Phoenix is limited in the number of different types of planes at the moment. Eg; It has 4 large 3D models with similar flying characteristics (slow 3D, large control throws) but no realistic flying scale type planes (eg Extra 330).

The Look of the models was better in Reflex, particularly the scale planes. The undercarrage on the Spitfire, Bearcat?, jets, with Phoenix looks like a cardboard cutout, does not turn and is way too small to be scale. Reflex had some very nice looking scale aircraft (Spitfire, F86)

Large Helis in Phoenix seem too stable and fly like the FMS Sim. BUT!!! Ive never flown those large Helis so perhaps that is how they handle.
The Smaller Helis in Phoenix are VERY GOOD. Trex450, Trex600, Raptors. The helis in Reflex were VERY GOOD too. I have a Trex450 and with a few tweaks I think it flies quite realistically.

The graphics in Phoenix are very good (as with Reflex) but Ive found I can turn my resolution and quality up to max (1920x1280) on my Notebook computer with Phoenix and it still runs very well.

The method of updating Phoenix is very good.
Phoenix seem to be very Pro active in there updates, so hopefully if something is not quite right it will be changed with a free online update.

I havnt seen the updated Reflex but the old version was very good.