This argument is a very old, very dead horse that has been beaten beyond puree into sub-atomic vapor.
As to the difference between a negative scan and a print scan - because of the nature of the two different types of scans (one with transmitted light, the other reflected), a scan of a print will inherently have more contrast problems than a scan of a negative. It's the same (but not as extreme) as making a Xerox copy of a Xerox copy... each additional generation of copying will lose shadow and highlight detail. The texture of the paper will interfere and cause certain amounts of contrast-killing reflections. This doesn't happen when scanning the negative.
Another significant factor is the skill of the scanner operator. Most consumers don't know how to operate their scanners to extract the maximum quality from their scans.
As David Goldfarb (one of our moderators) said, the decision was made to allow scans of negatives with the proviso that they are labeled as such, and that any manipulations performed are only the ones that would be possible/required to make a wet darkroom print. It may not be exactly the same, but if the guidelines are adhered to, then you get a fair sense of what the photograph would look like if wet printed.
If you feel the burning need to see better representations of original photographs, as previously mentioned, join some of the print exchanges. Otherwise, everything you look at online is at best a second-generation copy of something.