Picture quality can refer to many things. The most common refers to the resolution displayed. Is the image displayed at 1 CIF, 2 CIF, 4 CIF, or D1? The best DVRs combine high frame rates per channel with high resolution. A top quality DVR such as an AD Intellex Ultra may be able to process 30 images per second for 16 cameras (480 IPS total) at 2 CIF. Compare these stats to the cheaper DVRs and you'll see the difference.