I agree with what raimius said.
I'm not sure what the lifestyle is at Falcon prep comparaed to USAFA, but I'd imagine that it's closer to the military and academy lifestyle than most AFROTC programs. I say "most" because SMC's are pretty rigorous as well. So like raimius said, how badly do you want the academy compared to just being an officer in the Air Force? If the academy IS your final choice, realize that it's a lifestyle and any years of ROTC/prep don't count towards your four years spent there. The prep school would be your best choice. If you realize that you want a college experience too (parties, more freedom, etc), then AFROTC at a normal college would be the better choice. In the end, you still end up comissioning as a second lt.
Just something I was told, but if you don't make it into the prep school, but still want to attend the academy, attending AFROTC at a SMC could give you a little more help getting into USAFA next year. I was told by an admissions counselor from USMA that it shows that you can handle the rigors of a military academy-like environment and it could possibly give you a few more points towards your WCS. However, you may decide to attend AFROTC at a regular college for the experience. It could possibly change your mind about reapplying. I had a friend who was set on USMA last year, didn't get in, said he was going to reapply, did ROTC at a state university, and it changed his mind. He said he realized that he really enjoyed where he was and decided against it. Fair enough. If you're not "happy" at the academy, you won't do well.
Best of luck.