I think it depends on water availability what u use.
Where I hunt there is not a lot of water so a nalgene and steri pen don't work for me.
I use a sawyer and when I cross water I fill my three L water bladder. I also have a 6 L bladder at camp that I use aqui tabs in.
The Steripen Classic is what I carry as long as the water is fairly clear. I use the prefilter that came with it if the water has chunks. I also carry aquamira drops for backup treatment. My scout troop has the Platypus gravity system and I like that as well.
There are a lot of different systems out there that all work "better" than others in different scenarios. My last trip I used a MSR bag with a Sawyer inline, and a Platypus Meta Bottle. It worked very well, but the water sources can dictate what will and wont work well.
There have been a number of excellent posts over the past 1-2 years on filtation systems. Use the Advanced Search tool on this site and you'll find plenty of resources/insight.
I literally own at least 7 different types of water filters. I am in love with my sawyer mini with a 64oz bag. By far the lightest, easiest to use. Second would be Katadyn Hiker, third would be Steripen.