I have worked a lot with both scanning and digital (Nikon D100), and I agree with Erik's statement: it depends. To my eyes, the two formats are now very comparable to each other in quality. They yield very similar results, but both have a slightly different aethetic flavor (much like different types of film). Some people prefer the look of one over the other, whereas some projects benefit from the use of one over the other.
For my work, I found that it was taking me 30-45 minutes per scan simply to capture the range of color and detail I wanted from transparency scans. This involved a lot of working the software, tweeking its variables, scanning, and rescanning -- all trying to get an image the "felt" similar to what I saw on the light table. When I first started work with the D100 -- pow! I was amazed at how the images right off the card were already what I was shooting for. Plus, by shooting in raw, I can use Nikon Capture to massage the images even further.
I love the digital workflow over scannning any day, but one is quite dependent on the quality of the RAW conversion software.
But this is much like you are quite dependant on the quality of your software when you scan. Personally, I have no issues with quality of conversion software -- I find that Capture does amazingly well for me.