The GRAYL GeoPress is a purifier: it removes viruses as well as bacteria and parasites. The LifeStraw Go is a filter: it removes bacteria, parasites and microplastics, but not viruses. Where tap water isn't safe, South Asia, much of Southeast Asia, Africa, Mexico and Central America, get the GRAYL. For hiking in Canada and city trips in Europe, the LifeStraw is enough.
Why viruses decide it
Hepatitis A and norovirus are the bugs that ruin trips where water treatment is patchy, and they're far smaller than bacteria. The LifeStraw's 0.2 micron membrane catches bacteria like E. coli and parasites like giardia, which is what you worry about in a Canadian lake, but viruses pass through. The GRAYL's cartridge is built to remove them too. Visiting family in Delhi, Dhaka or Lagos, or backpacking in Vietnam, that's the difference that matters.
How they work day to day
The LifeStraw is a sip bottle: fill it from the tap or a stream and drink through the straw, nothing to do. The GRAYL works like a coffee press: fill the outer cup, press the inner one down, which takes about eight seconds when the cartridge is new, and you have 710 ml of purified water to pour or drink. That means you can fill a kettle, brush your teeth or make baby formula with it, which a sip bottle can't do.
Cartridges and cost over time
The LifeStraw's membrane lasts up to 4,000 litres, years of use, though its carbon filter for taste needs changing after about 100 litres. The GRAYL cartridge lasts about 350 presses, roughly 250 litres, or three years, whichever comes first; when pressing gets slow, it's time. Keep the GRAYL from freezing: a frozen cartridge can be damaged.
Weight and packing
The LifeStraw is the lighter one, about 250 g empty, against about 450 g for the GRAYL. Through airport security, carry either one empty and fill it after; both fit the side pocket of most backpacks.
Our call
If your trips include places with unsafe tap water, buy the GRAYL GeoPress: it's the one that protects against everything. If you mostly travel in Canada, the US, Europe, Japan or Australia, the LifeStraw Go is lighter, simpler and cheaper to run. Neither replaces your travel vaccines, and sealed bottled water is still the safe fallback.