So, what I am saying is that we all seem to see what we want to see and what bothers some is what the others are calling perfection so let's just agree to disagree on this one.
What you are seeing is at least partially an optical illusion, that would be illustrated if you had the position track (like the tracking camera data from the WC threads). The effect you are describing, in either case, is the discrepancy between the pitch attitude and the track. The "pitch around and slide" effect you note is a function of the angle of attack. The track is not right along the fuselage in either case, the difference is you can easily see it on my airplane (ex post facto) because of the nature of the design (and the way it is being flown). Mine turns pitches up abruptly right at the beginning and stays there, the flapless airplane swoops a bit so that you don't get a very sharp change from the nose to inside the track of the turn.
Also, the wing loading is probably a lot higher on my airplane. At the time of the video, the wing loading was about 13.55 ounces/square foot. Guessing at typical weights, the flapless airplane is probably more like 11 or possibly less. For a given turn radius, the flapless airplane has to have less coefficient of lift than mine. The difference is, to get that, it has to pitch the entire airplane around and hold the nose "inside" the turn by a corresponding amount. My flapped airplane has to do a bit of that, but it also gets some AoA from having a cambered airfoil with the flap deflected, so it's *probably* flying at a lower body angle of attack than the flapless airplane.
Note that making the flaps proportionally larger would reduce the angle of attack even furthers, and the "narrow flap"/"wide flap" issue can have a marked effect on the way the airplane looks in the corners. In fact, as early as the late 50's, people had realized that the Nobler turn didn't ever look very tight, whether it was or not. The Shark 45 was originally unnamed and had the word "Humbler" typed on a piece of paper stuck in the canopy. It had much smaller (proportionally) flaps than the Nobler and was known for a sharper turn. Bob Gialdini even mentions that to "make your turn more snappy, like a Shark" trim a good fraction of the flaps off his erstwhile Nobler clone Olympic. Ted Fancher took the experiment to its logical conclusion by making his flaps *variable sized* and doing experiments.
Of course, part of this is also piloting. I can't recall how hard I was trying to hit the corners in this video, compared to normal, but I absolutely, positively, guarantee that I was not attempting to achieve the full capability of the airplane. In the few cases we have good data for, I would guess it would turn maybe 1/3 to 1/2 the normal radius I am attempting to achieve. It can clearly turn much tighter (I have been flying essentially the same design for about 20 years, I have a *really good idea* what it can do and not do). I have no idea how hard the flapless airplane was attempting to turn compared to it's capability. Somewhere this is a video of me flying the Skyray, that would be a better comparison. I am generally very close to maxed out on those flights.
Note that the flapped airplane, no matter what the actual radius, will tend to look a lot better doing it, and can do it in an otherwise competitive package- that is, competitive in National competition. Aldrich figured it out in 1951, if you are going to get judged for appearance, you had better put on a good finish on a pretty airplane, and those weigh something, so design the airplane to handle this, instead of designing "max performance" airplanes with silkspan and a few coats of dope to seal it up, or severely compromised "flexible fliers" with hypothetically high performance, but changing wildly from second to second and day to day.
The "narrow and long" VS "wide but partial span" is a different point, this is about how much additional Cl you get VS how much hinge moment you require.
Brett