Well since this tread is about a Linux host with windows guest processes, I would recomend Wine over a virtual PC.
(not that I used Wine ever, but what the heck...)
If it would be the other way around.....
Let's say. Windows XP home with Ubuntu installed in a VirtualBox VPC AND as functional as I let it be.
Then a Virtual PC would be recomended. (and fairly enough RAM. Around 256MB min. for the ubuntu box)