The setup: buy the 0.50–0.60 delta call, sell the 0.30–0.40 delta call, 30–60 DTE, on a stock with a moderate bullish thesis. Typical risk-reward: $1 risked to make $1–$2, with probability of profit around 40–50%. Better than a naked long call when IV is moderately elevated — the short call's premium offsets some of the long call's IV decay risk.
When to choose bull call spread over long call: when IV rank is 30–60 (mid-range), when you have a clear price target above which you don't expect the stock to go, when capital efficiency matters more than max profit. When to skip: when IV rank is very low (long call alone gets cheaper) or when you have very high conviction and want unlimited upside.