Cross-sectional momentum — the only strategy that compares names against each other rather than against their own past. It buys a symbol when it ranks among the universe's strongest performers (and is actually rising), and sells once it drops well out of the leaders. Answers the allocator's real question: of everything we could hold, which is best?
"Difference" is strategy return minus simply holding the asset. On short, mostly-rising history these strategies tend to win only where the asset fell (they sat in cash) — real edge needs more data and choppier markets.