We can't get the Papua pouch in the UK, so Aquapac are the most used. I've tried several other brands and a few cheap eBay specials, and aquapac are working well.
The main thing is, make sure everything is lined up before closing the two cam locks, don't force them closed. I use an additional plastic bag as a back up, just in case it leaks during a session.
If I see any moisture in the aquapac, it get chucked in the bin and replaced. The won't last for ever, but so far, mine have lasted four years.
The main weakness is the crappy standard arm band. They are thin, feel flimsy and don't stay in place. I made a couple out of much thicker and wider neoprene. They make a massive difference, no more flapping around and the stay in place. If you look around, you'll find something to butcher up to make an arm band with, an old wetsuit etc.
P.s, I've seen pictures of Kato's Perspex pouches, the look brilliant.