First congrats to you and all HSSP Type 1 winners - certainly getting a type 1 out of HS for AFROTC is competitive. It's something to be proud of.
OK - Which is more selective? Probably Air Force over Army (best guess) statistically. Which is more valuable/ coveted? IMO, Army over Air force - here is why.
I think every AFROTC winner should be aware that your scholarship is basically a 2 year scholarship, and then you have to be invited to advance and finish training and commission. For Army, Navy all options, there is more of a fairness factor - meet each of the standards - keep moving forward. Ultimately my DS received all 3 scholarships - got the AF 4 year HSSP first, but given their cast-aside mentality of starting with more than they need, meh, I'm glad he chose to train to be an officer through one of the other programs. He has a military bearing, strong interest - I knew he'd try to commission and serve. Didn't know where though. A lot of those people AFROTC cut 4-5 years ago had near full rides that they gave up to use the AFROTC scholarships. Then when they were cut those scholarships from the school etc were no longer available. sca---rew---ed. Also, research which Army or other ROTC branch schools might offer you room and board if AFROTC will not. Examples - outstanding grades, no write-up, by all accounts active AFROTC cadets are not invited to move forward after 2 years - I'm talking MIT and Cornell undergrads with near perfect grades, for a real example - all based on the needs of the Air Force. It's IMO cold and a careless practice. That said - if you want to fly an AF airframe, love the AF mission - space or regular, or want to serve in cyber or whatever for the air force, then pursue your dream and take your chances. Just be aware you might be cut anyway and be out on a lurch and after grinding it out to meet their standards.... But you do you - pursue your own dream.