Most reviewers of the current generation of DVD recorders are united in their approval of the quality of picture that most all DVD recorders can now produce, verifying that there is not much variation between the units manufactured. You may want to pay attention to repair records however, as you don't want an expensive repair bill or loss of use due to a return. Panasonic has a particularly admirable frequency of repair record, RCA and Apex do not.
There is a quality difference however, in the mode in which you record your video. Like the EP and SP on your VCR, there are higher quality modes that take up more disk space, and lower quality modes that allow you to record up to 8 hours. Industry reviewers note, however, that when you get beyond two hours of recording on a DVD, the picture quality degrades significantly.
The recorder will begin to record only every other horizontal pixel and the individual objects on the screen lose clarity. When you get to the resolution for a six hour recording you are only getting every other vertical pixel as well, and picture noise is magnified. Sometimes movement on screen becomes annoyingly jerky.