Yup there is no doubt that vector programmes are really great on many levels. I used Vectorworks (mac) for years for work, but I hated it (because it was for work). I would consider going back to vector programmes now if I can find a good free one that works with both mac and PC, but despite the horrible memory usage gimp does pretty much everything I want and suits my painterly not-very-exact style.
Do this: export you next map at 100% quality jpg. Then export it again at 85% quality jpg. Upload them both here, noting the file size (the 100% will be almost double the 85%), without telling us which is which. I bet no-one will be able to tell.I export into jpg, I currently use max quality though