For me it's bin cages and most of the cages I have are RUB bin cages.
I find that they work best for me because they stack well and the plastic is hardwearing. The main reason I like them is that they can be tailored, when meshing to how I want them and what I want to hang in the cage. For example all of mine have a roof panel that can take a Fuzzbutt hammock and side panels for the corner crushes which are very popular with my Chinese.
Not only that but when you're not using them you can use them to store stuff in if you don't need them to be watertight. I currently have hamster toys in one of my spare bins and some bags in another.
