I would take into consideration what they can filter down to. The Platypus filters down to 0.2 microns, the Sawyer down to 0.1 microns. Neither of these filter viruses. I'm no expert on the subject, I've only done a small amount of research.
Simon a bloke in the woods has an episode on his water filtration systems which is well worth a watch. The one that stands out in his video is the Lifesaver Liberty which filters out viruses, and according to Simon, although I haven't actually found the specs on their website yet, the Lifesaver filters down to 0.015 microns.
It has some really cool features like, it can be used like a normal water bottle, you can attach a larger, external water bottle, it has a built in manual water pump and you can attach to it a scavenger hose. The filter is good for 2,000L.
Simon does say in the video that he doesn't like to use a 0.1 micron filter around agricultural land due to chemical runoff etc. I'm still doing my research on particle sizes for farm chemicals but did find this in a study carried out in the Mediterranean.. 'Most of the pesticides (such as
carbendazim,
tebuconazole, chlorpyrifos-ethyl and chlorpyrifos-methyl) were accumulated in the ultrafine-fine (<1 μm) and coarse (2.5–10 μm) particle size fractions.'
Maybe the subject of particle size has already been discussed on this forum, or other forums. It's probably worth having a search around.
