When talking water cleansing, no one system does it all. You need to know the threats where you are going to be hiking. Iodine, aqua mira, halazone and other chemicals kill all water borne pathogens as does boiling. But these do not remove heavy metals or harmful chemicals. There are many places where naturally occuring arsenic is present as well as even more places where mining or manufacturing has contaminated the water.
A good filter, one that filters to six logs (99.9999 % or > 0.2 micron) will remove heavy metals, all bacteria, and even some virus's. Some filters even have an activated carbon section to aid in killing virus's as well.
All this being said, most mountain waters are safe to drink raw. Tests have shown that running streams and even high traffic lakes are relatively clean. However, it only takes once getting ghiardia or cryptosporidiosis to make a believer out of you of the necessity for treating water. Rather than getting dehydrated, drink and take your chances of getting sick. Dehydration can kill you in a few hours but the incubation rate for waterborn pathogens is at least 72-96 hours.