Before this turns into a great bun fight let me have my pennies worth.
I am a consultant and I have also spent time on a fire truck. My abilities when I assist a client come to the fore and the benefit of both knowledge gained from books and experience enhance the level of service I can provide. To be a consultant you not only need experience that is gained from the sharp end but you also need to have very good communication skills so that you can get your point across to your clients. No matter how much you know if you can't transmit that knowledge to your client orally then you will fail!
I know fire-fighters that are very good at there job but will never be consultants because they cannot communicate effectively. I know consultants who have degrees and work for large fire consultancy companies, again they lack communication skills so would never make it on there own. However, you will always get good and bad in any profession. The only way to be sure that the 'consultant" has the experience and knowledge is to become registered, i. e BRE, IFE, etc. Even this will not be fool proof but it is a start.
Without a doubt, my experience on a branch has given me a different perspective than perhaps a university graduate may have. I am now constantly immersed in legislation, books, technical manuals and the like but that is the nature of the beast.