What should you be aware before making a choice?
That is a vague question. But still.
Choosing 3d modeling software is personal thing. There are number of softwares available and many of them have big number of features. So you should try demo of every one of them, try to model something more then simple, and whichever "clicks" is the one for you. Except for the price feature.
You have popular max and maya but are pretty expensive. you have as good houdini (with good free version, 'apprentice') and XSI (which is as good and cost less then max and maya and from personal experience has best workflow of all)
and there is free blender for which also has all the "big" features, and is free. But it's UI IMHO is unintuitive. But it's free.