I prefer stainless bottles and commute and tour with these and will also grab a Powerade or two on most days and once those have been emptied will refill these a few times and then recycle them... the Powerade bottle is nice as it has a no spill lid.
If I am carrying the maximum for a day's riding, 2-3 bottles will be stainless, one will usually be my stainless thermos full of tea, and I'll have a couple of Powerades and keep one in the cage and the second stashed in my bag. Works out to approx 4 litres / 1 gallon of liquid refreshment and on 100 mile rides on hot days I will come home on vapours.
If I am commuting and plan to be on my bike where I can refill my water 1-2 bottles (stainless) is enough.
A benefit of stainless is that you can flush them with boiling water which is a good sterilizer and if you are camping, you can heat them and their contents up.