It depends on your viewing preferences and the content you plan to watch. If you're a cinephile or plan to use the projector for high-quality video content such as Blu-ray movies or streaming services like Netflix, a 4K UHD projector can offer superior image quality and more details. However, if you're on a budget and mainly use the projector for casual viewing, Full HD can still provide a great viewing experience. Consider your needs and budget before making a decision.