I have both. There are pros and cons to both. You have to ask yourself what exactly are you looking for in a cutter, how much time do you want to invest in it (there's a big learning curve w/wishblade unless you know how to use a drawing program such as Illustrator), and how much are you looking to spend in the long run.
When I bought my wishblade in March, I was thinking it would be my only major investment. I almost sent it back after the first few days of playing with it. I was that frustrated with it. If you are considering this machine, I would highly suggest you join one of the many wishblade yahoo groups and read, read, read. Most have tutorials on how to do certain things. Another plus is many people offer cutting files for free (with some restrictions). There's lots of talent in those groups. The more you read and understand before you get the machine, the better off you will be. Once you get the hang of it, the basics are fairly easy. My biggest problem has been learning to use the Bezier tool in the Create and Cut software. Tracing in the wishblade software isn't too bad, but the more complicated the drawing, the harder it is. If you know how to use a drawing program, you should do well wtih it. The possibilities are endless. Even though I still haven't learned everything about it, I don't for one minute regret that purchase. I love the fact that I can cut just about any TTF in sizes ranging from under 1/2 inch up to about 8 inches. I haven't purchased any kind of lettering, with the exception of some rub-ons that I got for a fantastic price, since I've had my wishblade. And, since I can put whatever it is that I'm cutting anywhere on the mat, I tend to waste less paper. Those two things justify the cost to me.
The cricut was a purchase I made with my mother. She just started to scrap and isn't too fond of her computer. But she didn't want to have to come to me everytime she wanted something cut. Bottom line- we bought it because it is easy for her to use, plus I wanted to be able to use the Disney cartridges.

It's nice that it's portable and easy to use. You don't have to draw your own things. The downside is you're limited to what's on the carts and you have to puchase different carts to get what you want (as long as what you want is available on a cart). In the long run, it can add up to a lot more money spent.
One last thing. If you are considering an expression, I would also suggest that you look at cutters that will cut bigger than the wishblade. paperthreads.com has a good comparision chart.
Good luck with your decision whatever it may be!
