I was in REI the other day and was trying to decide between the Steripen Adventurer Opti and the Sawyer 2L Filter System. I went with the Steripen because it was more compact and lighter. However I have since been having second thoughts. The more I research it seems like the Steripen is not as dependable. I'm about ready to go exchange the Steripen for Sawyer since I have not even taken it out of the box yet. Should I do it? Which of these two systems would you guys choose for backpacking in the US.