Yes the Sat+ is less light, though it can grow 90% of the plants in the hobby without a problem.
The different in the lights is the amount of led's used to achieve the rated par. The finnex uses A LOT of small led's across a board, which gives off a lot of light directly under the fixture, and diminishes very quickly. I took my own par readings of the finnex lights, and they're par claims about light at 15-18" were correct, but my graph was much different than advertised on how intense the light actually got, so the manufacterur claims i believe are skewed quite a bit. The current usa fixture, marineland, build my led, etc, all use fewer leds, but more powerful leds, more power means the par will not diminish as quickly, and par is much more progressive, similar to t5's dropoff.
Can you kindly explain what you mean when you claim "my graph was much different than advertised on how intense the light actually got". Does that mean our noted PAR results are significantly more than what has been advertised according to what you have recorded? If so, and our numbers are indeed off, I will need to get our manufacturer to get updated readings for all of us.