Ha! It's funny, I've got each water treatment listed so far. I like the Aqua Mira drops more then tablets, works much faster- plus I think it makes the water taste better. The Katydyn Tabs- like Fal'er said, great backup- compact, simple, but take a while to work. The Pur Hiker- had it for years, great, reliable design, I like that I can connect the hose for a water bladder and pump water in without taking my pack off. I just picked up two of the Steripen LCD units. My local Dick's Sports had them on the clearance table for about $32, so I bought the only two they had. Sawyer's got a system with a mylar bag that looks good, lightweight and simple. With everything except the Pur Hiker I use a bandanna over the water bottle openings, as a pre filter.
One last thought, if you go with tablets, remember that the treatment times can vary based on water temp, I try to put a note in with the tabs if they are not in the original package.
Hope this helps.