I've always used bottles
a plastic and a metal one
personal preference, I prefer the lower centre of gravity and counter balance they provide, and easy to top up in streams too.
I also prefer their versatility over bladders on multi-day treks into the hills. You can use them to measure ingredients, the metal one is rated to allow you to boil water, saves carrying excess stuff in the rucksack (more weight, loss of efficiency, increased fatigue) and you don't have to worry about shouldering either.
Like I said though, personal preference.