When you're looking at shoe storage cabinets, one thing that will stand out in terms of your options are the different capacities you're offered. Typically measured in number of shoes, these capacities give you the option to cater your future shoe storage cabinet size to something that will truly work for you.
The different capacities generally on offer are measured in units of ten---so, you'll be able to pick up a shoe storage cabinet that holds 11-20 shoes, 21-30 shoes, 31-40 shoes, and 40+ pairs of shoes.
If you're wondering how to pick the best one, there are two basic strategies. The first is simple: Go count the number of pairs of shoes you have. Once you've found that number, round up, and buy a shoe storage cabinet with a capacity slightly larger than your shoe collection. (If you know that you have fewer shoes than normal, or are about to acquire a large amount of new shoes, size up accordingly.)
The other option is to stick to the amount of room you have. The details and dimensions of the products you're looking at should be listed. First, measure out the room you plan to put your shoe storage cabinet, and then purchase a piece that is slightly smaller than that dimension. If it does not have the capacity you need, you can use it to store your most commonly used shoes, or consider downsizing your shoe collection.