For me, this type of question also tweaks me because the candidates are not thinking long term.
The reality is 4 yrs in ROTC is a cake walk compared to AD. It is not 24/7 365 days a yr for at least 4 yrs. Life will be crappy for you if you entered a ROTC because they were the only ones that offered a scholarship.
You need to think about AD life and what you would do in the branch as a career?
Let's be honest, if being in a tank is not your idea of fun, than don't go Army. If being landlocked, and no intention of flying is not rocking your world, don't go AF. If the idea of sailing the oceans blue makes you turn green, and not with envy, the Navy shouldn't be on your list.
Yes, there are jobs that overlap in all 3 services, but what doesn't overlap is their missions. They are all unique and you should think about that when you decide which route.
DS1 applied AFROTC and that was it because he could not see himself in any other branch. DS2 played with the idea, but only for Army, no other branch was in the equation.
I am not saying that this is right for everyone, but if you don't know which branch and you are basing on prestige, I think you need to investigate.
Now to answer your question about which ROTC is perceived as the most prestigious scholarship. I would have to say NROTC. They are the most selective. They have taken both parts of AFROTC and AROTC to create their program. 85% go to STEM (AFROTC) and they assign a school (AROTC). As a sophomore if not on scholarship you vie to be selected for contracting...something akin to AFROTC EA.
AFROTC looks at the Whole Candidate when awarding any scholarship, I believe A/NROTC too. There is an actual % breakdown for each section. PAR is 60% for AFROTC, intended major is included here. It will include your SAT/ACT, cgpa, rigor of curriculum, class rank and school profile. 20% will go to ECs, and 20% to recs, PFT, etc.
As stated there is just no way to game the system.
AFROTC is the only one that does not tie the scholarship to the school, the recipient can take it to any college that accepts AFROTC. Only 5% of scholarships are Type 1 (no $$$ limit). 95% of these recipients are Tech majors. Think about it if you are non-tech, you have 5% chance of 5% to get that golden ticket. The number is incredibly low. Historically they have over 5K scholarships, and only offer less than 1K. That means 50 are given Type 1, and only 2 or 3 are non-tech out of that 5K pool. 85% of the AFROTC scholarships are awarded to tech majors. The bulk of non-tech come from Type 7 (IS tuition rate...can go private, but it can't exceed the cost of an IS). They make up 25% of this pool. Type 7 is about 70% of the scholarships. Again, do the math, you are looking at about 200 non-techs out of 5K.
Every ROTC is the same, SR yr EC's are not in play, it ends with your jr. yr. I do not know about A/NROTC, but AFROTC does not superscore SAT/ACT. It is the best sitting.
Hope that helps. Good luck on your journey!