I haven't got that much personal experience with the Platypus though I use their 4.0 gravityworks. I have yet to have any issues with it nor have those I have come across. Heck, this past weekend there were 3 other groups running the same set-up. I'm the only one that was using the carbon-filter (turns out there is no taste in the water here to filter so I'm leaving it at home next time).
I have, however, heard a few issues both on the forums and in the field of the sawyer system blocking easily and not wanting to back-flush or clear. The platypus as long as you follow the directions works great.
(start the flow, let about 1/4 liter or so come in, reverse it to purge the system of air, then it flows quickly. When you are done filtering back-flow about 1/4 liter to clear it out. That's it.)
On two occasions, I have had Platypus Big Zip containers develop leaks, usually along one of the folds. Interestingly, I have never had a standard Platy 1 or 2 liter water "bottle" develop a leak even with hard use. The leaky BZ's were circa 2005 and the issue may well be resolved now but I know that once upon a time they did develop leaks, easily.
For a simple water bottle I see no reason to carry a Nalgene when a recycled pop bottle is equally sturdy and a third the weight.
I use a Sawyer Squeeze, the larger version of the mini. I have had no problems with it in two years of use. And, that is with the original, failure-prone, bags.
I've never tried but I have heard that Platy threads leak with Sawyer equipment. Evernew bags do mate with Sawyer filters, or so I've been told.
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