I have the sawyer because of it's advertised longevity, it's field serviceable (i.e. back flush), it's relatively lightweight and (a biggie for me) doesn't require batteries.
Yes - it is true that a sawyer does not neutralize as many "cooties" as a Steripen ... but for where I hike it's not that big of a concern.
And yes, a sawyer's not quite as convenient as a Steripen, but the no battery thing makes up that difference for me.
I use my sawyer in a gravity feed set-up
Platy (unfiltered) -> hose -> hose clamp -> Sawyer -> hose -> water vessel