There's a pretty big difference, IMO. I have the Silhouette and LOVE it! The Cricut takes cartridges, so you have to buy each font, and the images. Silhouette will cut any font, and any image, so you don't have to buy them. You can buy them, as QuicKutz releases new images each month. It's a lot like the Wishblade . You do have to hook it up to your computer. I think it just depends on what you really want it to do.
the lowest I have seen the cricut is about $199 and the sillouette is $369 (machine plus a free 20 digital download card) quite a bit more, but I think you can do more with it. oh and cricut only cuts paper 6" wide (so far, I guess a wider one is on the way) and QK does up to 12"
With the Cricut it's cheaper up front but you're locked into their cartridges. But it's more portable and easier to learn.
With the Wishblade , Silhouette and CraftRobo, they cost more upfront but there's nothing else to buy. You can use ANY font that allows the outline feature. Not all TTFs do. You can also share files that you create with others and vice a versa. That's allowed in the WB forum here, by the way.
You will have to buy more blades and mats with any of these.
I do prefer the larger cutting area of the WBs. Plus being able to use just Xyron backed papers.
I think Michaels still has the Cricut for $139, sale ends today. The only reason I went with it rather than something that attaches to the computer is because I think I'd spend more time in front of the computer deciding which fonts to use than I would scrapping. At that point I need to move on to digital scrapbooking .