My UV experience is mostly with the UV Aquastar. Have also used the MUV and the Steripen...uh, the two-battery skinny one.

Even though it's bulky and susceptible to breakage, the first is the easiest to use because you agitate the water by inverting the whole container instead of stirring, stirring, stirring. Of the three, only the MUV failed (I returned three). So from my sample of N=1 I have no qualms about Steripen. I've just decided I prefer gravity filtering.

Cheers,
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--Rick