Out of the seven rigs I currently have running 3 are water and 4 are air. Air is much cheaper to buy and easier to assemble (though the Corsair H50 is changing that
). Air also takes up less space but newer water-cooling products are making inroads here as well. For a little more money the Swiftech MCP Drive units take up a little more space but are a whole water loop in a relatively small package. No way to get around the size of the rad, though. In the end the laws of physics win and a single fan (or even single-sized push-pull) will only remove so much heat. At some point a double or triple fan
cooling area is needed for higher heat loads.
There's no denying the better performance of a good custom loop (or it's cost and assembly time!) but as we move forward I expect to see prices on good air come down (the Sunbeam 120 CCT is already
very reasonable) and compact water cooling products take over the price-niche of high-end air coolers.
This is a thing of the past. Anti-freeze is no longer required if you're careful about your components. In the past aluminum components were more predominant than today and we needed anti-freeze to keep down corrosion but manufacturers got the message and switched to copper & brass. For algae/bug control you can by a silver coil to insert in the loop (or better yet, silver barbs!) and run nothing but distilled water. No danger there to pets or humans ...