Why the difference? Part of the reason is that the Invesco Momentum ETF is a long-only portfolio—it has no short bets that can go against it. The rest of the difference can be attributed to the timing and frequency of its rebalances: The Invesco Momentum ETF rebalanced only twice a year in March and last September, while the earlier-mentioned long-short strategy does it quarterly, the latest ones in February and last November.
Momentum investing usually involves a strict set of rules based on technical indicators that dictate market entry and exit points for particular securities. Momentum investors sometimes use two longer-term moving averages, one a bit shorter than the other, for trading signals. Some use 50-day and 200-day moving averages, for example. The 50-day crossing above the 200-day creates a buy signal. A 50-day crossing back below the 200-day creates a sell signal. A few momentum investors prefer to use even longer-term moving averages for signaling purposes.