RE: FS One Versus Real Flight??
My first Sim was FSOne. I learned to fly with it and haven't had a real crash when my buddies and family have had several. FSOne teaches the plane orientations and stick movements very well. It does not have the best or most accurate flight characteristics but it will teach you to fly.
I also have Phoenix and have been flying it for about half a year. Let me start by saying that I like it a lot. For normal fight, the flight characteristics seem more realistic than FSOne (for the models that I own) and it has better graphics and more planes than FSOne. It also navigates through the menus and options much faster. For helicopters they seem to have the physics figured out better than FSOne or Real Flight. Now that Horizon and Phoenix have some sort of partnership, the horizon models are included. (For me that was great since I have eflight, JR, and Hangar 9 models.)
With all of that said, I've been spending quite a bit of time at the LHS demo-ing RealFlight. I'm going to spend the money and buy it. For normal flying I like Phoenix, but for 3D style flight I think the realism is the best in RF and I like the way you configure things in RF better than the others. I really like having so many models and flying sites available. Although I think they are gimmicky, I like the combat and multiplayer capabilities. They add some fun to the "training" that I do on the sim.
If I had to do it again, I'd spend the money on RealFlight and all the expansion packs from the start.