Rita, welcome to cgarchitect!
One important step in approaching the 3D world anew, is to try and hammer out your educational goals as specifically as possible. There are several major differences between software packages, and tons of subtle differences. Chances are, you won't be able to address many of the subtle differences until you get some first hand experience. The major differences however, can be addressed largely before diving in.
1. What are you going to be using your models for?
If you're just modeling to view them on screen, or make 3d prints of, you won't need to worry to much about peripherals such as render engine integration or material editor capabilities. If you are planning on rendering your models, try and determine the degree of realism you are looking for. If you want to get as real as possible, you'll want a program such as 3ds max, which has great integration with VRAy ( a very powerful render engine ), a powerful material editor, very decent scene management, and both nurbs and poly modeling. That being said, 3ds max is a BIG program, and can do just about everything. It is, however, seen as being somewhat of a swiss army knife, in that it does a lot of things well, but few things amazingly.
3DS max is a polygonal modeling tool (its nurbs support is weak) and isn't always suitable for the management of complex types of architectural components. Revit is a large-scale BIM project management type program, which I understand to be used by a lot of commercial architects. I don't personally have much experience with it.
Rhino 3D is a very powerful program, and their support is unbelievable. I've actually had the President respond to my emails before, and my questions were anything but urgent. Rhino lacks a lot of history support, in that you can't go back and edit previous steps. There is some native support through the "record history" function, but it's not really easy to keep focus on. Now, something any architect should be aware of, is the free plugin for Rhino called "Grasshopper3d" (grasshopper3d.com). This is the most powerful parametric modeling tool I have ever used, and it is able to do anything! It is very efficiently coded, and has a tremendous support forum. It's really a program in and of it's own, but as things stand, it's offered as a free plugin.
If you are considering selling your models, you should be aware that most marketplaces show a high demand for quad poly models, as opposed to triangulated meshes. Programs like 3ds max and maya will allow the creation of quads, and rhino, sketchup, and others will output triangulated meshes. Rhino does have support for UV mesh modeling, but it isn't close to being considered friendly to use.
2. OS
Unless you can't afford a windows machine, you'll want to ditch that mac. If you are a linux guy, you can piece together a pretty decent 3d package, but you won't get photoshop (the only thing keeping me on windows.) Maya & Vray both have support for linux, and there are several other programs available as well.
3. Extras
I spend most of my time rendering furniture models, which are given to me from designers which have modeled them in Rhino. So straight out of the gate, I have to make a choice of rendering within Rhino, or outputting to another program. I usually work in 3ds max with vray, so I output my Rhino models as triangulated meshes, and then import them into 3ds max. There are hitches sometimes, but it usually works well.
From there, most all other scene assets such as rooms, curtains, trees, grasses, or other contextual models are ones that I have created within 3DS max. So, my scene gets to be a bit of a mix-matched arena, which 3ds max handles well. (well, kinda well...) I've played with Vray for Rhino, and the UI is god-awful, and the release version is way behind 3ds max. The standard in many industries is 3DS Max & Vray, but I've noticed that shifting lately.
I hope some of this helped!
ps. 3ds max & vray also have the most available support in online forums, which helps alot when you are starting out.
