Hydration bladders are a great and useful hiking tool. They allow you to sip water while moving and not have to remove your pack to access a canteen or water bottle. But, there is a downside. They can be punctured. You could slide off the side of a trail or trip and take a mechanical fall, rupture your hydration bladder, and lose some or all of your drinking water.
But I am going to argue that I believe that having an old fashioned hard canteen is a good idea to carry a reserve of water in a container; one that is not likely to rupture in a fall, such as a stainless steel bottle or canteen.
As well, a metal canteen [single walled] can be used to achieve a boil and disinfect water you gather from questionable sources, such as streams. You can chemically treat your water in a canteen and then transfer it to the bladder, and then gather more water and add tablets to treat it as you hike.
Nalgene [plastic] bottles are fine, but you can't easily do a boil in one, although I have seen people boil water in plastic bottles. A sunlight U.V. disinfectant treatment is a possibility with a clear bottle I suppose.
Carrying a small bottle that you can add flavored drink mixes too is handy and doesn't contaminate your entire drinking water supply, if you want plain water later, such as for cooking. I like the military Pilot's Flask, a 1-pint plastic kidney shaped bottle. It easily fits into a pants back pocket or cargo leg pocket. HAWAIIAN PUNCH low sugar mixes are handy for making crappy tasting water more palatable.
It's not a bad idea to carry a GAW [Give Away] bottle, in case you come across someone on the trail who has run out of water and is desperate for water [which I have encountered]. It also gives you yet another backup source of water, just in case you burn through yours faster than anticipated. We never know on a particular day, how weather may change and our body's need for water may change as well.
Finally, assuming you have told someone where you are going and have given them a time to expect you back, you will likely be found within 48-72 hours, IF you have stuck to your hiking plan and searchers have a good idea where to start a search. In that instance, hydration becomes critical, and if you have no means to treat water and are forced to drink raw water from a stream, it's likely you'll be recovered before any illness onset. As it is, most waterborne illness is temporary and uncomfortable, but not likely fatal.
Just a few thoughts...
[Bushcraft Woods Devil]