I've tried several different ones an it depends some on how you want to use it...
1. I like having a good reminder to drink often and don't mind a little weight on my back - so have used a Camelbak with their standard 3L bladder. In some places with larger gaps, I've even put a second bladder in my Camelbak pack, though sometimes picked a competitor.
2. If I was usin it more to carry water in my panniers, MSR makes a nice durable set of water reservoirs, I believe Dromedary is the line. I also had one from Sea to Summit but wasn't as durable as MSR. On a ride across Russia we used a 10L MSR bag to fill up at end of the day e.g. in a village and then cycled another 10km before camping. That bag was very durable to jostling around those 10km segments for a longer trip.
3. For use mostly in camp (or in hotels) where I was filtering water, I tried a set of 5L SOCATER water container bags ($10 for 4 5L bags). They served their purpose in Madagascar and still use in local camping trips here in TX. One did spring a leak. But as an inexpensive store a bunch of filtered water around camp they worked well.

In summary on my back I'd lean towards a Camelbak or clone - and as a durable one to carry in my panniers I would consider the MSR.