I've used the Omniseal plastic bags before. Durability is a matter of use. Don't let them get cold or freeze. I was handling a frozen bag (in a friendly way) and it split at the seam (used as a map case). Another broke at the seal. My experience is that they get brittle when cold.
Although the Aloksak says they are waterproof to 60 metres, I have problems keeping the one supplied with DRPSK and the one in my AMK FAK in a sealed condition. But then again I managed to get water into my 75m "waterproof" watch while going swimming so take that comment with a grain of salt!
For my money, ordinary ziplocks work pretty well for me... sometimes doubled up for safety.