I have one of those Topeak large bottle cages kicking around in the shed, and am thinking about putting it on the bike for the forthcoming tour in Ladakh. There's enough room for either two normal cages with my SIGG aluminium 750ml bottles, or the large cage with a single 1.5 litre plastic mineral water bottle. I'm leaning towards the latter, a single large bottle, because that does leave some room in the frame for my pump and a small frame bag full of tools, but I expect I'm missing an important reason to carry two bottles rather than one. (I'll have a few Platypus bags in my panniers)
What would your preference be?