Watercooling can be better in terms of bang for the buck so long as you don't upgrade the components often. Usually you won't see a huge improvement between generations of parts in any type of cooling, especially with technology being pushed to the max as it is right now. You need a few years to see a big improvement. An SP97 and an XP90 perform very closely, but the newest TR behemoth is better by a good few degrees. The biggest difference between these coolers are the sockets they can work on. The SP97 isn't going to work on AM2 unless you do a lot of hacking and cutting and even then it may not work properly. Waterblocks on the other hand can be used on newer systems with the help of an inexpensive hold down you can buy or make from bar stock.
Really what it comes down to is your buying habits. Buying the newest heatsink every time one comes out is expensive but some members do that and don't see any problem with it.
Really what it comes down to is your buying habits. Buying the newest heatsink every time one comes out is expensive but some members do that and don't see any problem with it.