I spent a 36 commissioned years in the Service and met all of the types mentioned in this thread (both commissioned and non-commissioned), from the arrogant a**holes to the best. The good SNCOs are the backbone of the Royal Air Force, and to have them on your side is the formula for success in any task. Time in the ranks is never wasted from the point of view of experience - there are many fine officers out there who know exactly what life is like for the young airmen and who look after them as if they were their own sons/daughters - not all officers are Wooperts.
However, from the highly educated individual's point of view, there are huge drawbacks. I have had a number of LAC's appear at my workplace with brains the size of planets and qualifications to die for, and witnessed their frustration at having to work through a system that works based on rank and time rather than ability; people who actively question procedures and get slapped down by their peers rather than receive the encouragement they deserve. Having trawled the fading memory banks, I can remember at least half a dozen who chucked in the towel in frustration, PVR'd and applied their qualifications to the world outside.
flch10000 - if your brother goes ahead and joins as an SAC, he will spend an increasing amount of time regretting that he chose that career path. He will become frustrated when he sees morons ahead of him progressing up the chain. He will become cheesed off at the lack of challenge in his life, frequently asking himself the classic question 'is this all that there is?'. And yes, every year in the Service will lose him commissioned time, time on much higher pay, quality of life and full time towards pension (it's all part of the equation). It will also lose him time in positions of authority, advanced engineering and management training, contact with industry, project management opportunities, opportunities to get to posts where he could make a real difference to the future of the Service, not to mention the networking opportunities to stand him in good stead when finishes his service and joins the big bad civilian world.
How can I speak with authority? My well qualified son joined the ranks despite all my arguments and advice. After 2 years he announced that he was bored with little prospect of job satisfaction in the foreseeable future and had applied for and been selected for a commission. A couple of years into his new career, over a beer, he turned to me and said 'you were right - I wish I had done this from the start'.
And he should seriously consider joining as a pilot.
Please e-mail me - I have detail not for this forum which might help your brother make his decision.