Here's my take. Although I've been flying for quite a while, I purchased a phoenix sim from an RCU member and have had it for a total of one evening so far. My intention was to practice muscle memory and also give my 3 yr old some sticks to move around and watch video planes go crunch; also as a learning aid when he's ready. I have no experience with the others other than the demo of RF and therefore will not say one is better. Pros of phoenix: looks good, the fight of the various planes seems real to me other than the absence of the "ground factor" and associated fear that plagues me in real life. If someone could sim that, they will have the best selling simulator, hands down. It works without stutter on my 3 year old sub $500 laptop (newest version of sim installed) at the medium graphic setting; only issue on med setting is a little less realistic appearance when floating on water. Free updates is a huge plus in my opinion; I know I will have an up to date sim when the kids are ready for some real lessons in a couple of years.
Gripes: I got it for planes and there is a noticeable lack of variety of standard Sunday fliers in the "40 size" range. There is a small selection of trainers and then a jump to large scale and performance planes. While it is definitely neat to learn how those handle, I would really enjoy practicing with the type of planes that I will normally be flying every weekend; the budget glow engine sport airplanes. I knew before purchase that I would probably like the plane selection in RF better. Also, the lack of a standard asphalt runway field with a good runway. I tried playing with the jets which don't seem to act as well on grass and there isn't any hard runways with enough airspace and room to learn landing correctly. Kudos to you jet guys, I just can't get used to the spool up time when needing power on approach.
Other than those gripes I think I will enjoy it and so far don't regret buying it over one of the others. The free updates is probably what sold me the most. Please take my apparently long opinion for what it's worth, good luck.