and running air tools is related to second stages and breathing how?
I see your point, which is why I suggested ether one to the OP. At most, only 2 people would be breathing off the first stage and one operating a BC, ether is adequate for that. The 17 is great for chilly diving and so is the 25. My point being that if I can breath off the 25 in 40 degree water and operate the air tools without icing, while maintaining the IP the second likes, then I consider the 25 to be of higher performance under load. The 17 does not ice but can't supply the volume the 25 does. The G250, G250V and the later model S600 (one with the chrome face and says S600 under the round purge button) are balanced, all metal tube and housing (Cold water) that is not that sensitive to IP swing. But when I use the 17 for the same purpose, there is a slightly noticeable change in the breathing efficency of the same second stage that I had been using for the 25 op.
I grew up, so to speak, on US Divers Calypso balanced piston firsts and unbalanced all metal seconds. The first stage under those conditions is critical to good performance of the second. Some of the other regs of the era, like Dacor and Scubapro, would under a load, cause you to have to suck for air with one breath and force feed you on the next. My presumption being that the first stage will have an effect on the efficiency of the second. So by using this equipment under far more adverse conditions that a sport or tech diver would encounter, establishes a set point for performance. Kind of like a fighter jet... If it can make 11 G turns without breaking up, while the pilot can only stand 6 to 7 G's without passing out, it is more than adequate for the purpose. However if the other fighters breakup at 9 G's, the 11 G fighter would be considered to be of higher performance.
So over the years as I started upgrading my equipment, I tried different manufacturers under these same load conditions. Scubapro was my choice for performance, maintenance and price.
