slack in the chain

Adjusted my chain today so it has 3/8 inch slack in the chain. This is well within spec, but it's much less slack than I usually do (the manual says 5 - 15 mm or .2 - .6 of an inch, and I've always stayed toward the high end of that range). I noticed that it "seemed" to shift smoother, which is what I was after. Anybody have an opinion on this? I know too tight a chain can be worse in some ways than too loose.

Keith