Some good points above. I have the Sawyer Squeeze and a MiniWorks. Like the Squeeze for simplicity and use, am looking at the gravity.
That said, none of the ones listed take care of alkali water - such as found in the Glen Canyon Rec Area. A number of Hayduke thru-hikers have complained of...
Just stopped in to say hi - I'm Dave, love mountain biking, hiking and have recently gotten back into backpacking. By recently, this past July. A 3 generation backpack in the San Juans. I think I just enjoy being outside, and the bike or the shoes are the tools to get me there!