I picked up a "life straw" on sale for $5 for my emergency pack
I hope to never have to use it as it would be for extreme emergency use only
Its light and packable iny first aid/emergency kit pouch and was cheap.
I figure if I have to use it I'll be in dire need and either be stuck in one place or wont care if I have to drink water I've filtered and spit back into a canteen
For normal non emergency drinking water filtration, get one with a pump or bag that attaches and then pushes water through the filter. I dont like backwash on a normal basis bit wouldn't care in an emergency
Bigger issue than what filter to buy would be to have a reliable/known water source..its sometimes harder to find the water than it is to filter it (depending on location and time of year)