Those faint lines are from your printer, I could be wrong on this, but I remember reading somewhere Canon printers did have a problem with vertical patterns forming on prints. Or it could be that you have a problem with your inkjet cartridge, it needs cleaning or alignment.
Regarding your main question, shooting raw is not necessarily better, capacity wise, as it produces 9.4 - 9.7MB files as opposed to smaller jpg's. But shooting in raw you get a bit of leniency in the highlights of a picture, meaning you can pull back just a tad bit more detail from highlights that would otherwise be blown in a jpg. Also, if you shoot raw you have the option to convert it to a higher quality jpg with less compression than in camera, using either the Photoshop plugin offered by Nikon, Nikon Capture, or a myriad of other raw converters out there. Personally I use Capture because of the batch feature it posesses, and its simple interface (I didn't like Bibble, another raw converter, for its complicated and non intuitive interface). I use the batch to process a lot of nef's into jpg's, using either auto settings, or creating my own set of parameters for conversion. The jpg's converted this way are almost twice as big (file size wise) at 4 - 5MB each as opposed to the usual 2 - 3MB straight out of camera. White balance too can be adjusted "after the fact", as well as noise reduction and better sharpening than in-camera. I use raw for my own shootings, jpg's on the job, and raw when I know I will be making big enlargements.