Climate control all the way. As another poster said, I also have had mine on permanently, set at 20 degrees for more than 2 years. I never need to touch it, cools the car in summer, warms it in winter. Never have foggy windows either. Modern systems make negligable impact on fuel consumption, in fact opening the sunroof is probably worse, due to the drag it causes.
Another benefit is if you suffer from hayfever or asthma, in the warm weather you can close the windows keeping the dust/pollen out and still be cool and comfortable.
There are still misconceptions among many irish drivers as to the benefits of aircon, some friends of mine have it in their cars and never use it!!
I'm familiar with the climatronic in VW's, very good system, but its a lot more expensive than the manual aircon (climatic). Problem with the manual system is that you still need to constantly adjust the temp, fan speed, air direction yourself manuallty, whereas the climate is brilliant for doing all this automatically.