That is the synopsis of the lecture I got when I turned in my final exam to the photography teacher I studied with in College. (Tom Petit - R.I.P.) He said I need to forget about technical things and concentrate on making IMAGES.
When shooting with a digicam, I always avoid JPEG and shoot in RAW if the camera I am using will support it. You are right. The RAW exposure and balance controls coupled with sharpening upon import will provide a superior picture. As much as possible, I try to use JPEG only as the final step in the process when I'm making the file which will be posted via the internet or sent to a client or other recipient. Better, sharper, clearer results will always be obtained, IMHO, when done that way.
According to the latest books (namely "Photoshop for Photographers" by Martin Evening) it is no longer necessary to use step interpolation to enlarge or reduce a digital image. If you are using the latest versions of Photoshop and you make sure you use the correct interpolation settings ("Bicubic Sharper" for reduction or "Bicubic Smoother" for enlargement) you can get good results from one single step instead of several smaller ones. He does say that many people still believe step interpolation is better but he says it is not strictly necessary, in his opinion.
As to whether a scanned photograph will beat a digicam image, I agree with a caveat: It all depends on how both images are imported at the outset. A crummy scan can not beat a good digital import from Camera RAW using a good quality camera but a good scan, done properly, can beat even a good image from a digicam if the user knows what he's doing.
The thing is that, once imported from analog to digital, a traditional photograph should be on equal footing with a digicam image. I do not believe that there is a magical quality in a traditional photo that makes it better than a digital image. The benefit only comes at the beginning of the process.
Like I said, I believe that the scanning process, itself, acts like a noise filter. I also think that a well done photograph can hold more information (detail and dynamic range) than a digicam can produce. The quantization process will capture more information than the digicam.
Does that mean that a photograph is always better than a digital image? No. It goes back to the image over process issue. The photographer has to ask himself what he's trying to accomplish and tailor his technical process to his goal. If he is trying to produce an ultra-sharp image that reaches out and slaps the viewer in the face, so to speak, he will probably need a traditional photography work flow. If he is producing graphics and images for a web page, a traditional work flow would be like shooting flies with a Howitzer.
It all depends on the image the artist is trying to produce.