The 600ml variety is rather handy on a hot day, and/or for when you're engaged in some ample walking. This product is not as re-useable as it used to be. The bottle used to be thicker, and that way it was less likely to crush in your handbag or gym bag.
The bottle itself is now made of thin plastic. This is great as this product is now much lighter to carry around on a hot day, however you're more likely to throw the empty bottle in the bin after only one use.