The main difference is that the 3000 has multiple patterns. Some of those patterns might sound better to you in certain applications and, of course, they make it more versatile if you choose to use it on something other than her voice eventually. I tend to prefer it, much of the time, set to figure 8, both for the way it sounds and for its superior sound rejection to the sides.
Having said all that, both Cads are still your basic cheap old-school Chinese mike with a high end bump that may seem shrill.
I'll sing into a mic the day I ride on a bic. Peanut Road