here some updates: basically as written by some of you already, it was mainly a scanning issue, and printing I'd say too.
I finally scanned the negatives through a V600, and apart from the calssical "bending" problem of negatives on the OEM support (I already ordered the upgrade from betterscanning, btw), I'd say the results are quite astounding, to my standard at least (and coming from the 35mm format).
Some photos now and comments:
SARD01_alghero parete fiorita
=> classical "bend" problem, focus should have been ok and the blurred bits are due to poor scanning, imho. Ektar 100
=> example of low light picture: it is indeed "soft", but in an acceptable way now, I believe. Ektar 100 film.
=> mixed light, image here is as sharp as I think it can get from actual workflow. Ektar 100
=> B&W example, with planty of light: razor sharp imho! Ilford HP5
=> B&W indoor, again pretty sharp despite the mixed light. Ilford HP5
=> Just an example of the enormous latitude the machine can get, I am astonished
all in all, I'd see no particular problem then, except:
1) scanning prints sucks
2) workflow is important of course, and hopefully I'll solve the film bending issue
3) printing manually is nice but imho the studio I use imho does'nt get it always right: I've seen a lot of prints with a degree of sharpness which is way below the one I obtained scanning negatives!
3b) printing also involves the idea of contrast/color correction etc => no real control on the workflow if like me someone uses an external studio