Autocad is by far the best system to use, unless you can talk them into a 3d modelling software, but its not really suited to architectural work.

I'm in the engineering side of things, but I used to work in an architectural office, and you cant beat Autocad. Everyone knows how to work it, and its extremely simple. I know there are a few companies that do add on packages too, so you can have everything in libraries (different wall constructions, doors, windows etc)