For 2 or more people, platypus for the win. It's all I carry now. The basic setup gives you 4 liters of water storage, it filters quickly and passively, so you don't have to camp exactly next to a water source. Fill it, hang it, get on with other chores. You can fill the reservoir in the evening and have water for drinking and cooking until the next morning. I also carry tablets in case the filter goes south. Problem with all the tablets is they are hell on your GI bacteria.
Steripen is cool and I have one I used for travel in 3rd world so I could drink hotel water, but they take a long time and you still are limited to the nalgenes or whatever that you brought for water storage.
