The field stop is above the 1.25"barrel. That means vignetting, though it is small, and it means a lot of in travel to get to focus.
As far as I know, the internals are the same across the brands, though the outside diameters and weights differ due to the different outers.
Unless your scope is a very long focal length (over 2 meters), the jump from a 17.3mm is 30mm in my book.
Think about the magnification jump. You want at least 50x between low power and the next one up in a 8" scope.
That's what I thought on the field stop location. With the minor difference between clear aperture in the barrel and the field stop diameter, I personally would never notice the vignetting unless maybe the APOV was very narrow.
For the mag steps, I agree with you under normal circumstances. For my case, I am just looking to maximize the field of view with a 1-1/4 eyepiece, but still keep the APOV as wide as possible. The 24mm it the focal length where the math works. Not many 20mm eye relief options, though, which is why I was asking the CN team. When I need greater exit pupil for more light, I move to the larger diagonal and 2" eye pieces.
Thanks, again. Very helpful.