I know you don't want to use Windows - but don't discount the ability for your MBP to run it - particularly for say Rhino. I wouldn't be to afraid of switching between Windows and OSX - you'll really just need to pick the tools for the job and run them however you can.
I work with a pretty well known international firm, and although we mostly use microstation we are starting to move towards to using Rhino a lot, with Sketch Up for quick work and the less '3d technical' people. I wouldn't bother with Autocad really - even though it's what most firms (in the US...?) use, you won't become a great architect by knowing how to use it. Learning something like Rhino will give you a tool that you can use to create whatever you can imagine. Saying that though - Ashlar-Vellum Cobolt seems similar to Rhino, and does run on OS X (I don't know if it's UB yet). It may be worth a look.
As for Microstation - Microstation SE was the last version available for Mac (and I think it was OS 9 only maybe, so it wouldn't even run on the new intel Mac's). Archicad is by far your best bet for architectural work on the Mac (imoo). I think there was also a new free-form modelling extension recently released for Archicad 10, which may also let you do Rhino style modelling without having to run Windows.
Good luck,
a.
