You missed a few cooling methods...
Basically, what a peltier is is a polarized metal plate with an electric current running through it that you attatch directly to the cpu. The polarity of the current causes all the heat in the plate to be drawn to the side of the plate away from the cpu. That side becomes extremely hot, while the side touching the cpu becomes cold. However, you need to combine this with some other cooling method, since if the peltier isn't properly cooled, the whole thing will become very hot very quickly, and it will fry your cpu. It also serves the function of eliminating the possibility of condensation on the cpu (and also on the water block in the case of liquid cooling).
Pros: VERY effective. Eliminates condensation.
Cons: REQUIRES a more standard method of cooling with it. If the peltier's cooler breaks down, your cpu is toast.
Or some other high performance coolant. Similar to water cooling, but it requires a compressor somewhere in the loop.
Pros: There are no more effective cooling methods.
Cons: And you thought graphics cards were expensive...
This is one I play on doing someday when I actually have a PC worth super cooling. Basically, you can get a decent sized minifridge for less than you can a high end PC tower.
Pros: Combined with standard air cooling, this is probably more cooling than the average person will ever need.
Cons: Requires a LOT of modification to the fridge. It's HUGE. It will use a lot of power.
Some misconceptions about water cooling:
- It's "EXPENSIVE" ; In the past, yes, but as it's become more mainstream, there are companies offering complet kits that are comparable in price to higher end air coolers. And to DIY, I consider www.dangerden.com
to be very reasonably priced for all your liquid cooling needs.
- Leaks will destroy everything! ; Yes and no. If you shell out a bit extra and get some distilled water, there's not problem. Pure water is NOT conductive. it's when you add all the impurities of naturally occuring and treated water that it becomes highly conductive. But since most people put in additives so the water looks cool with their case lights, make sure everything is pressure tested and in good shape before putting it in the case.
- Unreliable (pump breaks down) ; If you set up a water system properly, you don't even need a pump. Admitted, pumpless circuits are not as effective, however, they are more than enough to keep your cpu alive until you can fix/replace the pump.
- Consumes a lot of power ; No. A small submersable water pump doesn't use that much power. A high end radiator draws no more power than 2 good case fans. A more standard radiator would use no more power than the fan in a standard air cooling solution.
Now, what is the "best" cooling solution? Depends how you use your computer. For an "average user" whatever comes out of the box will be fine. Same goes for a recreational/avid gamer; unless you have a newer P4, or an older Athlon. If you live in warmer climates, these have a tendancy to shut down from overheating for many games. If you're doing any overclocking, you should invest in a water cooler. While you may be able to overclock with a good air cooler, you will prolong your cpu life with water. Even the worst pumpbased water cooler will be more effective than the best air cooler. Now, if you're cracking government mainframes, you probably already have a $2000 quad (or more) mobo, and the cost of nitrogen cooling shouldn't be an issue.
IMO, the one that gives the biggest bang for your buck would be water. Even under average use, the increased cooling offered by a water cooler will prolong the life of your cpu.