Pushing a shear load over threads isn't great for the bore, so we prefer a plain shank.

another day in paradise, or is paradise one day closer ?

The shank also sets the stud installed height.

The full size shank helps with alignment.
And heaven forbid that something goes wrong and the stud sees a bending force the shank will stand up better.

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P.E. Metallurgy, consulting work welcomed

Fully threaded is probably "worse" in all applications.
If you are concerned about some flavor of "strength" it strongly suggests deciding based on some rule of thumb may be quite risky.

However, I think the (low) potential loading could EASILY make it a moot point.
If a conventional stud is not available so must be custom made, some really nice "all thread" might be a very good alternative.
https://www.mcmaster.com/threaded-rods/high-streng...

In addition, IF there REALLY is a strength/fatigue/?? issue, AND the assembly design cannot be modified to use COTS parts, THEN an engineered reduced shank fastener might be far better.

For some applications full threaded are preferred. They are more-or-less required in ASME Sec VIII, Div 1. If you are going to tension a stud by measuring elongation, full thread is the way to go, unless the stud is machined to provide constant area.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand