The Zalman is better than the Thermaltake because it has better heat dissappation with the copper fins while the Thermaltake looks like it just circulates air more than anything. Also, depending on your rig, the first one is best if you have a good side fan to blow fresh air into it while the second one will blow blow the hot air into the rear exhaust fan but probably requires more of a roomy case.
(Consider fans from a science point of view. Look for a good thermal conductive metal with heating piping that effectively channel into a large surface area.)