Over here there are three main manufacturers, Plastimo
(France), Vetus (Netherlands) and Can (Italy).
I have all 3 on board.
In comparison, so far the CAN wins.
ones I have came with the boat
and tend to leak at the fitting and split along the edges. Material is a translucent film liner with a fabric
cover. Edges are welded but only once.
The tankmaterial itself is not textile reinforced.
No 3rd connector for vent.
Vetus & Can both use thick fiber reinforced material with double welded edges.
Material wise robust.
CAN wins, as they weld in a connector plate while Vetus relies on a customer attached press fitting which tends to leak. CAN has a vent connector which is desirable to let air escape when filling. Doing this through the filler is unreliable in my view.
One thing I do not like on the CAN is that the welded in fitting seems to be not very strong. Time will tell how well that lasts.
I'm any case put some thin foam or netting under the tank to prevent chafe. One way to secure them is adding a strong net over them.