I started with sizzix a LONG time ago. I have THOUSANDS of dollars worth of dies that cut ONE SIZE.
I got a cricut and LOVE it. I can cut lots of shapes in any size I want.
Each machine has pluses and minuses.
IMO, the cartridges are cheaper than the dies and you get more versatility.
Personally, when my cricut dies, I plan to get a cameo or gazelle. I like being able to use my own shapes (I was one of the lucky ones to get SCAL when it was able to be used on a cricut) and not be tied to specific sizes/shapes.