From my personal experience with similar filters of each type, it is due to the survival filters being able to be cleaned. The survival filters clog up after about 10-20L of lake/river water being put through. After they clog they can be cleaned, either with water or chemically. House filters, on the other hand, are much more complicated and generally can not be easily cleaned thus they basically last longer but are one use.
Also survival filters are usually more expensive.
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