I'm running a SARD tank and it was well worth the money. I would say my water temps dropped a good 5 degrees after running it. The second one looks to be of nicer quality but they'll both do the same job.
as the ad states their designed to sit above the factory cooling system, the swirl pot removes all the air bubbles from below that point hence improving the cooling of the engine. Used normally on extremely high powered race engines so its a gimmick to the normal man, but they do look tricky : ) Its up to you mate