Ultra HD, or 4K, describes a camera recording roughly 8 megapixels at 3840 by 2160. It provides more pixels across a scene, which helps wide views and distant detail, and it costs proportionally more bandwidth, storage and processing at the recorder.
Four times the pixels is not four times the usefulness. Whether 4K helps depends on how much of the frame the subject fills and whether there is enough light to use those pixels.
Where 4K earns its place
Wide areas that one camera must cover, such as a parking lot or a loading yard, benefit most. A tighter 1080p camera on the same subject often matches it for identification.
The cost at the recorder
Higher bit rates consume disk and network capacity, and decoding several 4K streams strains a workstation. Check recorder throughput and storage before assuming a camera swap is enough.