To minimize dust in the case, you need to have filters on your intake fans and make sure that you have positive pressure inside the case.
This, in general, will result in increased noise.
Alternatively, just use a dust buster once every few months to clean the inside of the case.
Edit:
To be complete, I have to add that if you have negative pressure inside the case, air will enter the case from every hole, including CD and DVD drives. Then, dust will enter your CD and DVD drives too.
So, there is definitely an advantage with a positive air pressure system. Except the price to pay is more noise for same cooling performance.
Too high a price for me!