My biggest concern in water treatment is obviously effectiveness of treatment. All of the Steripen products seem to work effectively against all of the bacteria/viruses I am worried about. So that's a good thing.
My second biggest concern in water treatment is weight of system. According to the comparison charts the Steripen Freedom is the lightest model at 74 grams. My question is, this model includes a cord to recharge the internal battery. I am wondering how much this cord weighs alone as I will need to bring it with me for 6 months or so on the Appalachian Trail. I am also wondering how much the pre-filter system weighs.