Absolutely a relevant issue. Sometimes air consumption is not truly the issue. I found out last season that a diver I helped certify had a proper SAC rate, but because of equipment differences, he would suck down his air twice as fast as I would.
The end result was that his el-cheapo hard plastic (we buy what we can afford right?) fins could not keep up nor were they as efficient as my Twin Jets, so I needed to slow down so the dives would last longer and be more enjoyable.
Otherwise, his air consumption was very close to my own.