When the computer was left at idle there was basically no discernible performance difference between the two pastes. So only load temperatures have been compared, using the Folding@Home client with one instance running on each core of my 5200+ at 3.2Ghz and 1.5v to generate the full utilization. CoreTemp was used to log the temperature of each core over time and the median temp of these averages used for comparison.
I also tried two different heatsinks, one made of aluminum and one copper, just to see if either thermal paste had any favorable reaction to a specific metal type. But other than the performance difference of the heatsinks themselves, the compounds maintained the same spread across both series of tests.
In all of the tests, there were only two instances when temperatures varied from the rest, and that only by one degree. The Tuniq TX-2 recorded temperatures that were consistently 1-3° C cooler than AS5. Whether you throw out the odd results or average all the tests, the TX-2 shows a clear 2° advantage over the AS5 at load.
Arctic Silver does recommend a "burn-in" time of up to 200 hours to get the full advantage from their thermal compound. In fact, the one test where the AS5 recorded the lowest temperature was the very first one, when the AS5 had already been in place for several days. But the difference was only one degree, and it is more difficult to guarantee identical testing environments when spread out over such a long period. Besides, the time involved in conducting such a lengthy test is far beyond the scope of this review.
Keep in mind that the two degree difference shown by the Tuniq TX-2 occurred while the CPU was at 100% utilization. Depending on how your processor is used you may or may not see a benefit from using TX-2 over something else. And the cost of AS5 compared to TX-2 seems to be about the same, around $6 for a 3½ gram tube. But whether you're looking for the best cooling performance, thermal compound that's a little easier to cleanup or maybe just an alternative to the usual gray paste, next time you're in the market for some I recommend you pick up a tube of Tuniq TX-2. I know I will.
Thanks to Sunbeamtech/Tuniq for providing the TX-2 for review!