Basically, the difference is the thickness of the dies. Sizzlits are really thin, so if you are using the regular die cutting machine, you need a converter, which just pretty much makes the die the same thickness as the original dies. The Sidekick is now out, which is made for Sizzlits and embossers. The original dies can also cut through a lot more materials than the Sizzlits. They can cut through rubber, felt, magnetic paper, and other materials. Sizzlits can just cut through one sheet of paper generally. Another big difference is the size of the shapes. Sizzlits are much smaller than the original dies. The originals come in a range of sizes, while all the Sizzlits are small. I'm really horrible at explaining things, so I'm not sure if this helps much at all. If you go to the Sizzix website, I'm sure that would help you more.
