I haven’t tested enough water filters myself to make any kind of serious comparison, and perhaps there is better product out there I have never heard of, but I can assure you, that if you are looking for something tested on humans that are satisfied and still alive, LifeStraw is the way to go.
LifeStraw is really light (50g), handy and easy to keep clean. The attached string is supposed to allow wearing filter around the neck I guess, but in real conditions having something hanging there and irritating your skin is not really comfortable. Instead, I found it really useful for drying. I would open the mouthpiece at the top and the bottom part too, and attach it to my backpack.
The first time you use it you may have impression it is clogged. It’s all good, don’t worry, you just have to take a few proper sucks to get the water flowing. This is also the reason why you would use a container to drink from, rather than, let’s say, a running stream. It’s just much easier and you would probably want to store your water in bottles/bags in case you may not find other sources (which is a reasonable strategy by the way). Remember to blow air through the filter after you are done and shake it well for a few seconds.
In terms of experience: I had water from lakes, streams, dirty, disgusting puddles of unknown origin, as well as fresh rain puddles with all sort of forest creatures swimming inside. It tasted great each time and I haven’t been sick so far. However, in some conditions this filter will not work. You have to know the place you are going to, because LifeStraw filters particles, parasites and bacteria only. It will not remove viruses or dissolved chemicals. Obviously, it will not desalinate water as well. Still, the best method, if you really want to be sure about what you drink, is to boil water for at least one minute. Iodine is not good for your thyroid gland and it will not really remove viruses anyway. Distillation takes time and some contaminants can be carried into the condensate. However, some regions are free from viruses in water and it should be pretty safe to drink as long as you stay away from cities and villages (sewage and agricultural contamination).
If you are a hiker like me, and you are not planning on testing your survival skills, this water filter is the right choice.
If you like any of the products mentioned above and trust my opinion, please consider purchasing through Amazon: