I've been using C4D since early this year and I have had great success with it. I am quite surprised at the performance issues you describe. I'm working on a nearly 4 year old mac pro with a X1900 graphics card
I'm not familiar with pc cards so I can't say if that is your issue but clearly your hardware is happier with artlantis.
I can say a few things ...
preview window:
- yes C4D can handle large models
I use 'gouraud' shading set to a high level of detail and no problems
I use the interactive render region tool A LOT (you can adjust the quality of this interactive render as well - to speed it up)
final renders:
- the quality that you can get out Advanced Render is truly fantastic (with the right settings and render time of course)
you can do vray as well
I also had a look at artlantis when I was considering a rendering solution but I chose C4D because it is in another league as an all-round package, and has more options to tweak and extend to produce better results. Also the sketch rendering is probably the best in the industry.
Artlantis has great appeal because it is optimised for architects.
However I would say that C4D is very easy to pick up. Just ignore what you don't need to use.
Have a look at
this Lynda coruse - I signed up for one month to do it and then cancelled - but it was excellent.