RSI and MACD are two of the most popular momentum indicators in technical analysis, but they're built for opposite market conditions. RSI is an oscillator measuring the speed and magnitude of price changes on a 0-100 scale, best suited to sideways, range-bound markets. MACD tracks the relationship between two moving averages and excels at identifying and confirming trends.
Traders compare the two because using the wrong one for current market conditions is a common source of false signals — RSI in a strong trend and MACD in a choppy range can both mislead traders who don't recognize which environment they're in.