The former of the two is a PC2-8000 kit available in 4GB configurations as a 2x2048MB kit, which will run at DDR2-1000 speeds. The latency on these modules is 5-5-5-18, while is ample. They do, however, require significantly higher voltage than standard DDR2 modules to achieve these speeds at 2.1V.
The DDR3 kit is also available in a 2GB or 4GB configurations. They will be using similar latencies of 6-5-5-18 at 1.85V, again significantly higher than the stock 1.5V of DDR3 modules. With voltages so high, having those expanded heatsinks is probably a necessity.