I am trying to think of the way I can store that is:
-Easy to store.
-Has the greatest chance of staying fresh for the longest time.
-Even if the water is not drinkable when I need it, I have the greatest range of ways I CAN purify it when I need to use it. (MSR pump water filter/Iodine Tincture or tabs/Bleach/or even SODIS.)
I think the 2-liter solution bears the greatest opportunity to utilize the stored water in a semi-urban environment that regular ol' joes like me can start storing right now with minimal investment.