I have done it both ways. 40 buckets is a lot of air, and a lot of stones that get clogged up. I have run over twice that many using just a lot of air at the reservoir(s), however you will need more movement of the nutes in each bucket. I am assuming you are using some kind of a drip system or some feeding system similar to waterfarm. In order to facilitate the movement of water you will want to CONSTANTLY run nutes from the res to the back bucket(s). Want you will want to accomplish that the water circulates from all the buckets CONSTANTLY. So, put a water pump into the res, and run a 1/2" line to the back bucket(s) forcing the nutes to move from the farthest travel distance back to the reservoir. You will have to play around with it, because you don't want to have the pump supply more water to the back buckets than they can return back through all the other buckets in the system or they will overflow. A lot depends on the size of the pump used, size of buckets and size of the lines interconnecting the system.
I don't think your buddy is correct in his theory because others including myself have lived with a bunch of stones in each bucket for years without doing any harm, but rather benefiting the room. The only reason I used the circulating system was because I was tired of cleaning and or replacing all the air stones.

keylime