Try several, and use the program (or programs - multiple) that you feel most comfortable with. I personally used Truespace and OpenSCAD for 80% of the models in my Shapeways shop, but I have since upgraded from Truespace to Blender.

Thing is, no one program does everything well. If I start from a 2d drawing of an item, I end up using at least six different program before the final model is done, leaning on each for their particular strengths.

Stony's rule of Adult Computer Education:

Take two software packages and two users. Give one program to one user, give the other program to the other user.

Wait six months, then swap the two pieces of software between the users.

They will BOTH think you are a hero, saying: "Oh, this program is SO much easier to use!!!"

It's not that either program is either better or worse than the other, what changed is the human.... they learned more about what their own needs are, and what they are comfortable doing.

The moral is: adults will not learn a piece of software until they believe that the software will solve a need they have.

Having said that... I'm an engineer, not an artist. Curves (such as automobile hoods) give me fits.. I could never draw a dog. But, I can read a diagram of a passenger car and produce a rather good copy of it.