Essentially, there are two common types of 35mm bulk loaders.
One type - the Alden (and various other names) is larger, has a film gate without felt, but usually requires you to waste an inch or two more of film for each roll loaded.
The second type - the Lloyd (and various other names) is smaller, has a film gate with felt, but usually requires you to waste an inch or two less of film for each roll loaded.
You will most likely find differing opinions of the various available re-loadable cassettes. There used to be more choice.
I like the plastic cassettes for the nature of the closure and the fact that only one end opens. I have older, Agfa cassettes that I removed a bunch of un-processable film from. They are metal, and have strengths as well.
It is important to be diligent about their use and maintenance.
Bulk loading is not nearly as "money-saving" as it might once have been, but I really like the flexibility it offers.