Only my personal (untrained) opinion: The goal of the modeling process should always be to describe a form within known tolerances ,with minimal math and maximum fairness. All three things are important. Your tolerances,I do not mean the units settings maybe “method of production” is better - will greatly impact the final look. Things milled in wood, possible with some secondary surface treatment (sanding,lacquer) will hide local continuity problems but a lumpy surface, which can be perfectly g2/g3 continuous is, in this case, a bigger problem.(Local continuity vs. Fairness)
Minimal Math means the simples Surface which is true to the design intend should be used. Usually we strive for pulled, smooth surfaces. Single span just has the benefit that it is always curvature continuous. ( If your cv count is one higher than our degree and all point weights are 1, your crv is singlespan If you can’t achieve a specific form in single span don’t shy away from multispan.(but use at least degree 5, as any lower can lead to kinks in your multispan-crv) For blends your first cv controls G0 continuity, your second cv G1 continuity and so forth. For mirrored srf G1 is sufficient as they are automatically G2 continous (maybe this is wrong )but most of the time your better of building a “bridging” srf over the centeraxis, as this is requires the least amount of cv and you dont have to match your half surface in the middle.
Maximum Fairness is arguably the most subjective of the three. 1. fundamental question: Maybe not every crv should have maximum fairness? 2. How do we define and perceive fairness? But usually this means a the change of curvature of curve should be monotone( or continous) over small and large distances. The simple way to put it how “nice” the curve is. To evaluate this it helps to look at curvature graphs and reflections. The reflections will move over the surface “twice as fast” revealing small “defects” like breaks, dipping, …
I hope this is of any value for you ( or others), again this isn’t anything that was thought to me so take it with a grain of salt, also some parts are probably lost in translation from german.
I also would like to hear how the rest of the community judges a “good” model .