Nothing rigorous, I based my power observations on the testing I was doing at the time… i.e. cutting 4.75mm plywood with, and without, air-assist. With the 2.8 watt laser, I was cutting completely through the plywood in 5 passes at 100 mm/min feed, full-power, focus at top of the material, and no air-assist. With “strong” air-assist from my 3-gallon compressor — and lots of noise — I could cut fairly well in 4 passes.
Then my 3.5 watt Banggood laser arrived in the mail. I set it up in the same machine and conditions… and saw virtually the same performance as I had with the 2.8 watt laser. So, where I had hoped to cut in 3-4 passes with the new laser, it took the same 4-5 passes I saw with the smaller… and I judged the two lasers roughly equivalent in power.