Excellent questions, Wendi. First, let's define some terms. Machine embroidery is usually divided into two categories: auto-digitized and manual punch. Auto-digitized means that you feed in the art, make a few choices and adjustments, and the machine creates the design for you. Manual punch means that you set the digitizing points, telling the program where, when and how to create the stitches.
A lot of what to choose in a digitizing program depends on what type of results you want and how long you can take to learn the program. There are some that have very little learning curve, but it shows in the "finished" product. In my opinion, that covers pretty much ALL auto-digitizing programs. Some are better than others, but none can compare to good manual digitizing.
Manual punch digitizing requires a lot more from the digitizer, and thus will have a steeper learning curve. As for manual punch programs, there are several out there, ranging in price from a couple hundred dollars to several thousand dollars. Obviously, the more expensive the program, the more "bells and whistles" it will offer. Some programs offer a trial download so that you can see for yourself what it can do. Others don't have this option. Are there any programs in particular that you have been looking at? You could probably be able to get additional input on any of them by asking specifically about it here.
I can tell you from personal experience about Embroidery Magic 2 (a very inexpensive - less than $100 - yet effective program, but you will need to buy a tutorial for it. I recommend Aunty M's tutorial, and if you buy them together, you can get a discount.) or about FancyWorks Studio by Pantagrams. I really like them both, although they aren't "master it in a week" type programs.
There is also Origins, Embird, StitchWorks . . . I'm having a brain cramp and can't think of any of the others at the moment. Anyone else want to offer input?