I have a platypus bottle and a couple of Evernew bottles (just got them) as well as a platypus Big Zip II (3 liter size).

As far as I can tell there is no significant difference between the bottles. The Evernew bottles come with a cap keeper which is handy and a shock cord for keeping an empty bottle rolled up. But other than that they seem equivalent.

But there is a big difference between the two approaches to hands-free hydration. Evernew offers a drink tube to attach to the bottle and the drink tube extends down into the bottle. The platypus Big Zip II has the tube attached to the bottom of the bladder. At first glance the platypus system seems superior since it's easier to get the last drops of water out of the bladder. However I have discovered that this has a serious drawback.

I've used the Big Zip II on about 10 hiking trips. Last week when I went to fill it up for a new trip I found that there was a leak, not in the bladder per se but in the hard plastic piece between the bladder and the drinking tube. In thinking about it I realized that since this piece is on the bottom of the bladder while in the pack's hydration sleeve it is subjected to a fair amount of force due to the weight of the water (3 liters) and the up and down bouncing that happens as I walk.

Now my model is not the newest one so this issue may have been addressed. However I have also decided that something like a Big Zip is not that convenient for backpacking. I had this idea that the large volume would mean I could carry all the water I might need in the Big Zip. But I found that it is ridiculously hard to get the 1 or 2 cups out that I need to rehydrate my food at for dinner (when not camped near a site with water). I tried pinching the bite valve but that is so slow that it's frustrating. And of course opening the zip closure and pouring out is problematic when you only need a cup or two of water.

So now I've switched over to the Evernew bottles and drink tube. Not that I have anything against the platypus company or anything. I think a playtpus bottle with the drink tube kit attached would work just as well. But I'm through with the specialized "hands-free" systems like the Big Zip.

Perhaps others have different perspectives or experiences.