I have the swiftech mcw5002. It is a well made block which is only bested by a few high-performance blocks.
The whitewater (or equivelent) with a special socket adapter is probably better at cooling (3C max) at the expense of more complicated mounting and higher cost. Do you want good watercooling or a spare-little-expense best-performance setup? Is a 2-3C temp delta worth an extra $30-$60? The answer usually depends on what you hope to gain from water-cooling.
With the good setup(5002), you don't require a great pump for good performance, but it doesn't hurt either. A great setup requires a high pressure pump for the high flow rate needed to take full advantage of the better waterblock; those are more expensive and/or larger.
Just be sure to use the largest heatercore that you can cram into your case. It'ill be a big benefit no matter which block you choose.
IMHO
