Camelbak.
1. I like the hydrolink feature. The removeable bite valve comes in handy for cleaning.
2. Parts availability. If you NEED to, you can run to REI, Popular, etc to get new parts. Sure, they will be the blue civilian versions, but they will work.
Get a Military Omega reservoir, which has a larger opening than the longneck that makes it easier to clean. I like 3 litre, but a 2 litre will work if you carry an extra source for long trips. The civilian versions are blue and come uninsulated. The Military version is black, has an insulated tube, hydrolink system, and a bite-valve cover to keep your grill free of mud when you take a sip.
I DISlike the hydrastorm for a few reasons.
-The tube screws on to the bladder, and these threads can strip.
-Parts are hard(er) to find.
-The bite valves do not let as much water through.
Check them both out first to make the right choice.
Oh, and do not get a camelbak carrier unless you really like a particular design. A bladder alone and a different carrier is the best choice. For PALS attachment, the BattleLab HPP is cool. For PALS/stand alone, the SDS (gag) Sandler is a GREAT buy for 19 dollars. It can be used alone or attached to a MOLLE/PALS rig.