With the announcement of the HTC One X, there has been a great deal of confusion about which CPU will power HTC's latest flagship phone. There are basically two versions of the HTC One X. One for worldwide markets which is powered by the Quad Core Nvidia Tegra 3 Processor and one for LTE capable markets, like Canada, which is powered by the Dual Core Qualcomm Snapdragon S4 processor.
To start off I think it's important to know WHY the North American Version of the One X will use the Snapdragon Krait S4 over the Tegra 3. LTE expansion and adoption in North America has been much more accelerated than in other parts of the world. Carriers, including Verizon, AT&T, Rogers, Bell and TELUS, have poured millions into the expansion of their LTE 4G networks, so it's only natural that they want devices that take advantage of their new networks.
One might wonder why couldn't LTE be included on the Tegra 3 version. The problem is that LTE wasn't supported on the Tegra 3 platform until only a few days ago. This certainly wasn't enough time for HTC to wait for LTE capable Tegra 3 chipsets. These are the reasons why there are two different configurations of the HTC One X.
The other issue that comes up next for most people is that conventional wisdom dictates that four Cores are better than two, but in reality there are far more variables in play. The Nvidia and Qualcomm took different routes in developing their current flagship processors.
Nvidia took their successful Tegra 2 dual core CPU and doubled down and made it into a Quad-Core (with companion core) processor. This strategy has allowed Nvidia to be agile in developing, manufacturing and shipping out their new chipset in a relatively small time frame for a relatively new ARM CPU manufacturer.
Qualcomm on the other hand decided to stick with dual core and instead try a smaller manufacturing process (down to 28nm from 45 nm). Qualcomm's strategy is mirroring how they improved their First Generation Snapdragons (found in Nexus One/Desire) over their Second generation Snapdragons (found in Desire HD/Incredible S/Desire S) by simply improving the manufacturing process (from 65nm to 45nm).
The other important aspect to consider is battery life, on paper, both approaches taken by each company make a lot of sense. Nvidia claim to excellent power management is with the fifth "ninja companion core" that handles all the trivial task of a phone/tablet using a much less power as it it clocked at a very low frequency. Qualcomm on the other hand is banking on the 28nm process making the processors much more power efficient by virtue of being more efficient per clock cycle. While it's hard to make a uniform scientific benchmark between the two (until the One X is actually released and can be benchmarked head to head using the same test) this should mean that both platforms will have respectable battery efficiency.
It terms of sheer processing power, the Nvidia Tegra 3 at full load (maximum usage) does more calculations per clock cycle than the S4 but the number of times that this would actually occur is very low since apps in general will not be programmed to specifically take advantage of four cores. This means in general overall responsiveness and tasks should be (and seems to be) equal. In GPU/gaming performance Nvidia does have a significant upper hand (especially in high end games) considering their history in Graphics. But in general, both platforms will handle the majority of games available on the Android Market.
What does this all mean exactly? Well without getting to much into details, this means that the Tegra 3 will be best for some tasks while the S4 will be better at other tasks and both have features that should lead to comparable battery life. In the end, one would be hard pressed to notice a performance difference between the two in either responsiveness or battery life.
To know more about the performance of the S4 Snapdragon versus the Tegra 3, we highly recommend reading the CPU head to head showdown article of Snapdragon S4 vs Tegra 3 by Anand Shimpi of AnandTech. We also recommend checking out his in depth review of the Qualcomm Mobile Development Platform powered by Snadragon S4.