Q: How big of a difference is 1.0 gain vs. 1.1 gain?

The percent of gain difference between 1.0 and 1.1 is 10%. A gain of 10% brightness is gained from the projector’s lumens output.   Example : If a projector has 1000 lumens you’d gain 10% if the material gain is 1.1. 1000 x 1.1 = 1100