Which type of voice mode is often used for long-distance (weak signal) contacts on the VHF and UHF bands?

Single Sideband (SSB) is highly efficient because it concentrates all of the transmitter's power into a narrow bandwidth without transmitting a carrier. This concentrated power makes it the standard choice for long-distance, weak-signal voice contacts on the VHF and UHF bands. While Frequency Modulation (FM) is very common on VHF and UHF, it spreads power over a much wider bandwidth and requires stronger signals for clear reception. Therefore, FM is not suitable for weak-signal DX (long-distance) communication compared to SSB.