I think the BigZ dies are bigger than the original machine. There may be some sizzlet ones that are bigger too??? At least that is how I understand it and you have to have the big shot to use them. I haven't seen enough of the BigZ's that I would want that I'm willing to spend the money on the bigger machine! Just using the original! The rest of the dies work okay. I've never had much luck with the converter so I bought a side kick (the older one) and they work fine. If one doesn't cut too well I use the shims from my QuicKutz on the back of them and then they cut better.
Did you know cuttlebugs work in the sidekick or with the converter? The cuttlebug kids do not work with these - they are too thin but they do work with the QuicKutz revolution.