To me, a baserunner is a baserunner. As a pitcher, you still let the guy on base. What's the difference whether it was a walk or a single up the middle?
A walk can be an arbitrary call based on a specific umpire's strike zone, and most plate umps have slightly different strike zones. Thus,
sometimes a walk isn't the fault of the pitcher's skill, so much as it can be a result of a subjective call from a non-player in the game. For instance, a pitcher trying to pick corners of the plate with one umpire might get three straight strikes called for him, or three straight balls, entirely depending on who is behind the plate.
A hit is more directly the result between the one-on-one "battle" between the hitter and the pitcher.
At least, that's the general argument behind it, or so it has been explained to me by the many pitchers I have played with (I also am a former ball player). Obviously, there is still luck involved in a no-hitter just as much as there is in a perfect game, the difference between a perfect game and a 3-hit shutout can sometimes be a game of inches so the slightest variance can have huge results, but pitchers love blaming the plate umpire for whatever they can get away with (former plate umpire here as well, by the way), so walks are sometimes played off as the ump's fault, not the player's fault.
There is more pride in a no-hitter because pitchers and players see it as more "pure".