I have owned a few boats in the class you are considering, although not the River Runner. For my money the best in this class is the 15 foot Klamath. It is welded, wider and deeper than the closest Gregor, and has a .080 hull versus a .063 for others. Mine was a very seaworthy and dry boat that I used way offshore in Queen Charlotte sound a few times, as well as on the Columbia and similar rivers. I ran mine with a 25 Johnson.
It held its value well, selling for about what I paid for it after 5 good years use.