I like both but like Jani, some bias may come in here....
What he stated is very true. I'd say that MORA is well known and renowned, for good reason: cheap, tough and the red handled ones are iconic
Marttiini is less well known and this is a pity. They offer a reasonably low cost puukko in carbon or stainless, fairly good range and a likeable knife for the everyday tasks. I've got a carbon one of theirs in grey stained birch, I varnished the handle out of preference. This is a super little knife, nice keen carbon blade, fat bulbous handle that offers fantastic grip in the wet or cold (better than MORA redhandle) unpretentious workman. As he said, decent sheathes on offer with these knives- The puukko dangler sheath is pure genius (other sheathes are simply inferior!) a tight tube lined with wood or plastic, then covered with quality sewn leather. These sheathes RETAIN the knife under all conditions, try upending one, it'll keep the puukko inside. You won't lose that out in the woods as you might with more conventional belt knives. It also is easy o access the knife fast and it wont stick in your ribs when you sit down.
I was idly thinking about what belt knife would I take plus a folding knife and my choice surprised me. I have a Marttiini Skinner which is a hybrid puukko. Nothing fancy here, good enough stainless that sharpens in situ in the field, a rubberised handle offering exceptional grip, a guard unlike a real puukko, gimping for grip and a very good tight dangler sheath. Yes, i've got 'better' more expensive knives including real puukkot, but this Marttiini is so versatile that it can really do anything you ask. I'd recommend any knife fan checking out these shy Finns as well as our noisy neighbours from Sweden!
Regards, Will