Both are bright 1080p DLP workhorses built for rooms where you can’t control the light — offices, classrooms, and daytime living rooms. The EH401 is the more modern unit: it accepts 4K HDR input, packs into a compact, genuinely portable chassis, and produces crisp text and detail for presentation duty. The PA503HD is the value play — similar brightness class with ViewSonic’s SuperColor tuning and a bigger owner track record, usually for less money. Moving between rooms or feeding it 4K sources: EH401. One fixed screen on a budget: PA503HD.