While it is true that if you are in USAFA it is easier to get a pilot spot then if you were in AF Rotc, it is also true that that is way harder to get into USAFA then it is to get into Rotc. So if you can get into either and you want to be a pilot, the USAFA is the more sure way to go.
Actually, that isn't completely accurate.
In the recent past, there were fewer AFROTC national scholarship appointments (300 per year) than USAFA appointments (1200 per year). Not sure what the numbers are now. For Navy it is my understanding there are about the same number of 4 yr ROTC slot as USNA appointments (1200 each). AROTC tends to award around 2500 scholarships per year with about 600 being 4 yr and 1900 being 3 yr vs the 1200 USMA appointments.
Now a days, it takes a "SA quality record" in most cases to earn a 4-yr ROTC scholarship. ROTC in fact is a bit more "merit-based" than SA appointments. The ROTCs rank order the applicants and draw the cut line.
For the SAs, the geographic diversity factor has a major impact. The #1 principle nom from a less competitive congressional district will get an appointment, while the #10 ranked candidate from a very competitive congressional district will not get an appointment even though their record is much better than the candidate that is the principle nom. This is why every year there are candidates that receive SA appointments, but don't receive a ROTC national scholarship offer. They did not rank high enough in the National order of merit. It is also why there are candidates each year with great records don't receive an SA appointment but do receive a 4 (or 3) yr ROTC scholarship.
If you are lucky enough to receive a SA appointment, be greatful, and humble. You got a lotto ticket. Make the most of it.