I've done 3 all grains now, and have always mashed at 1.5qts/pound grain. Is there any benefit to going thicker or thiner. The math is just easier at 1.5
Thinner mash generally requires more time and is not going to hold temp as well. Too thick and the enzymes don't get around enough (I've been told). I do 1.2 qts per pound. More a matter of personal preference, do what works for you