I love using my primes, no doubt they give exceptional quality. You also have to learn when to use a prime and when a zoom becomes a more practical choice. The output quality of today's zoom lenses is very good. Now if are a pixel peeper and you want to look at the images at 200% you will find some differences. I have enlarged some shots up to 24X30 from my 1DMKII using the 24-70 lens and I was overjoyed with the results, even from a couple of feet away.
There are times when a zoom is just more practical, when you have to recompose on the fly and you don't have the opportunity to either change lenses or move yourself. I was shooting a world cup downhill race and I was using my 135 f2. I was finding that the racers were not always coming off the jumps in the same spot and you could tell in advance (maybe 20 seconds) of what spot they would be coming off of. The 135 worked well for the one side but on the other side, they were too close. I switched to one of my zoom lenses and was able to get the shots the way I wanted.
While in general the primes will give you the better results do not discount the value of the zoom. In the hands of a good photographer either one will give you results that your customer will like.



