The better sims are expensive but if you are serious about RC flight they will definitely save you money in crash expenses. That said, everything has it's place. The free FMS simulator will help with learning the controls in different orientations, getting used to the aircraft coming towards you and your controls being reversed. I have been able to fly an aircraft in FMS and have it "bounce" off the ground and back into the air and continue flying. Trust me, that doesn't happen in real life
But if you just want to get a feel for the controls it has it's place. There are a few other newer free sims that I have not tried myself so I really can't comment on them personally. For helicopters there is HeliSimRC and it has very good physics and is fairly true to real flight characteristics but it is heli only and no selection of models to speak of.
I have never used Clearview so I can't comment on that. Clearview is in the middle price wise and I believe you can download a demo to try it out before you make a purchase.
How good inexpensive sims are really depends on what you are expecting to get out of them. Do you want to learn basic controls in different orientations (going away from you vs pointed towards you) or do you want to practice 3D or aerobatic flight and use it as you progress to learn more complex manuevers?