They are different systems all together.

If you just want water that's biologically clean then the tabs are ok.

If you are unsure, or know there are chemicals in the water source, then you want a filter IME.

Even the SteriPen,et al do not remove chemicals, so keep this in mind, depending upon where you tread on YOUR trips <img src="/forums/images/graemlins/smirk.gif" alt="" />

The weight trade is also a health trade IME.
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PEPPER SPRAY AIN'T BRAINS IN A CAN!