We love the steripen - we have two now. I've never used the Sawyer squeeze, so I can't comment on that.
We find the process of filling our bottles and sterilizing them easy and fast with the steripen, with a few caveats:
The trickiest part is to learn the flashing light system and what to do if you get a red flashing light, or if it's hard to see in bright light. But we got the hang of it pretty fast.
It takes 45 seconds of holding the pen in the water bottle and swishing it around for a 1/2 liter bottle of water, or 90 seconds for a 1 liter bottle of water.
We have the Adventure Opti.
Interesting. We used the SteriPen in Nepal up to 17,000' the first trip, and 15,000' the second trip without malfunction. Maybe we were lucky. I did take spare batteries.
I would agree that it's a better for fast moving, clear water rather than stagnant, cloudy water.
My 2 cents: SteriPEN is perfect for near-alpine moving water sources (like mountain streams and lakes)... not ideal for low-altitude stagnant water sources (like low-land lakes and silty desert springs). It doesnt filter, just sterlizes, so the water needs to be fairly clean to begin with.
Last time I used a Sawyer squeeze was on a backpacking trip as a backup filter (...our pump broke so it became our primary filter). After +/-15 L of filtration the filter began to clog through normal use (very clean, moving water) and eventually became nearly impossible to use. My take-away for the sawyer squeeze: great for 1 person for a small packpacking trip (2-3 days).
I have a SteriPen and love it. I agree with the other responses that it does nothing to filter the sediment from the water so you want clear water to begin with. I actually filter my water first with my Platypus and then use the SteriPen - probably overkill but that's okay with me.
I used the Sawyer to filter "cow" water....standing/stagnant, surrounded by cow hoof prints. We were out of water and desperately needed water for the next climb....so we put the sawyer filter to the test. We never got sick, so it worked!!!
I have a steripen too but didn't have it with me, although it wouldnt have filtered the particulates out like the sawyer did.
lots of ' makes sense' comments here. I used to use the steripen, and liked it very much, but...batteries would die unexpectedly or it would malfunction. But probably the biggest reason I stopped using it was switching to smart water bottles with the narrow opening to save weight. There's also the filter vs purify issue broght up here, but normally, 99% of the time you'll find 'clear' water to purify, or you could use your bandana or something to 'filter' particles.
REI member since 1979