Welcome to Apug!
We are comparing apples to oranges as the the Digna came with different lenses/shutters:
from a a quite basic combo like that of better box cameras but with the focussing feature!
to a medium class lens/shutter.
As for the body
the Digna models have got a releas on top of the body, the Subita has got it at the lens.
Typically basic tube-cameras are lighter than folder cameras.
Folders always are more compact.
The viewer seems the same in all models.
Just start using your model, then look around locally where you should be able to get such cameras dirt cheap.
Thus you may find out what suits you best.
I would advise a model that got a shutter with several times and apertures (as the advanced Digna model).
But there are countless models of many manufacturers...
With bellows there is the issue of them being punctured. (Especially with Agfa folders. Bellows might look pristine when buying but develop punctures after a few closings.) Go into a dark room, put a tiny flashlight, with open lamp, into the bellows and inspect it from the outside.
You find many advises on bellows repair here.