Curtain (night & day ). I feel complete dark room is very conducive for night slp & can use day curtain for naps.
I have blinds and the strings are a strangling hazard when they are older. And with blinds, lights still come in. Can never achieve total dark room which I regret . And If wind blow (fan or natural wind), the blinds will sway & hit the wall & produce noise which might wake baby.