To the first approximation, use || when you want to find the first true value in a list of values, and use or when you want to do logic on the results of expressions. The or precedence level was added specifically in order to do logic on the results of list operators without requiring them to be turned into function calls with parens. Hence or is generally used as control flow between "almost statements", and typically reads better for logic within a boolean context too. The || operator is mostly relegated to picking fallback or default values, and in fact much of that usage will end up using // in the future instead.