Stainless steel cages are way better than aluminum ones. The aluminum cages lose their grip over time, wear down from the bottle, and put black marks on the bottles. Some years ago, I considered plastic or carbon cages, but I thought they were slightly difficult to put the bottles back in while riding along. And they are barely lighter than stainless cages.

I've used similar cages to these for more than 10 years, still working great. blackburn chicane. I most always use Camelbak bottles.

This style is easy to slam the bottles back into the cage without looking down. I've never ejected a bottle, since the steel works like a spring to hold tight.