First let me qualify my opinions. I haven't tried the Sidekick, but I have the original machine and dies as well as Sizzlets & the converter.
I understand hesitating at the expense of the larger machine. I did too. Even when I was looking for a C'mas gift for DDIL I seriously considered if the Sidekick wasn't the way to go. This is the cheapest prices I've seen for the Sidekick other than using a 50% coupon, which makes a difference. Usually it was only ~$2 less than the original with the coupon making the big one seem not too bad.
The Sizzlets are very easy to use with the converter...no trouble at all. I really like the Sizzlet alphas & would probably never buy one for the original. However, I looked at their site & frankly there aren't all that many dies for the Sidekick yet. I like the ability to use dies from both.
The biggest drawback for the original machine is its weight. You really don't want to have to lug that thing around!
As for what other dies will work with the Sidekick, I've only
heard that it will work with the QuiKutz and/or ClickIt. The Sizzix site says this:
"Expanding the uses of the Sizzix Machine and the Sidekick, the Sizzix Adapter allows crafters the creative flexibility to use other brands' thin dies in their Sizzix Machine as well as their Sidekick. Each 2 3/8" x 2 5/8" Adapter is made from the same high density plastic material affixed to the back of Sizzix Sizzlits. The Adapter is available in packs of 10 for convenient, ready-to-go die-cutting of multiple shapes."
I'm not sure where else to get the information.
Right now I guess it doesn't matter (for me anyway) since the adapters have been listed as "out of stock" for a while now.
)
