Maxwell is very good.. but it is an unbiased renderer which means it produces physically accurate renderings but takes more time to render than biased renderers like Vray or mental ray.. so it's a real pain to render animations
Learning maxwell is quite easy though because it's unbiased, you don't have to fiddle around so much with the settings
In architectural visualization, Vray is widely used because of the relatively fast render times and photorealistic quality. And it is used mainly in 3ds max because it was originally made for max so the max version is the most complete one; the maya/rhino/sketchup/etc versions are beta or do not have all the functionalities..
If I were you i'd stay away form form z. In my experience, form z is good only for precision in CNC milling
I would recommend 3ds max + vray (maybe because i use them
) for interior designs but again all of the other major 3d softwares (Maya, 3ds max, Blender, XSI, Modo, Cinema4d, Lightwave ) are very good too
BUT these softwares cost a lot of money, so it's good if you work in a company or if you can get educational price..
Blender is a very good FREE open source 3d software but has a very steep learning curve