When I first started doing all grain, I was using the "standard" 1.25qt/lb ratio. After about 6 months, I switched to 2qt/lb and my efficiency went from the mid-high 70's to the low 80's. I've recently done ratios at 1.5/lb and my efficiency was just over 82%, so not much of a difference with 1.5/lb and 2/lb. I haven't gone back and tried a mash of 1.25/lb, so maybe it was something else that changed my efficiency, however, the grist ratio was the only factor that I changed.
Also, with my batch sparge/ cooler system, when I use 2qt/lb I get equal amounts of first runnings (mash) and second runnings (sparge). When I was using 1.25qt/lb, I was getting a much lower amount of first runnings than compared to the second.