The H2D is the printer Bambu positions as a full digital workshop: true independent dual extrusion (soluble supports, two materials without purge waste), LiDAR-driven calibration, a much larger build envelope, engineering-material temperatures, and optional laser engraving/cutting up to 40W. The P1S is a 2023 single-nozzle enclosed printer that happens to cost $399 right now.
If you are asking which one to buy as a first serious printer, the honest answer is the P1S plus an AMS plus a year of filament, all for less than half the H2D. The H2D makes sense when dual-material printing, big parts, or the laser module are concrete needs, not aspirations.