the dual core CPU does not currently outperform the tegra 3 (for both CPU and GPU)
The per core performance of the snapdragon CPU is much higher than the per core performance of the tegra 3 CPU and because most applications for android are still single threaded, the snapdragon CPU offers better performance.
If you were to run a game or some other process that is heavily threaded, then the tegra 3 would easily beat the snapdragon as it has a faster GPU and an overall faster CPU in that case.
The android OS while it can handle multiple cores, it is designed to use 1 core as much as possible in order to save power. Furthermore, most applications will go into an idle state if you send then to the background (background processing requires it's own dedicated code in android and very programs need it so it is still rare to activate more than 1 core even when running multiple single threaded programs. (While this lowers performance a little, android is designed this way to extend battery life (the performance lost from this is barely noticeable only really noticeable in benchmarks)
if you do multiple single threaded tasks such as downloading a torrent while surfing the web, then you will notice android push 1 process to another core if the first core is hitting 100%
In my experience with tegra 3, it is very hard to actively use more than 2 cores in a non gaming environment because I simply don't know enough programs that remain CPU intensive while in the background.
Overall, I believe that the snapdragon CPU is a far better choice than the tegra 3.
Even with my HP touchpad (running a snapdragon S3) gets a quadrant close to that of the tegra 3, (also gets about 70% of the CPU performance of the tegra 3.
The snapdragon S4 has a little bit faster CPU performance, and significantly faster memory performance (more than twice as fast as the snapdragon S3, and much more GPU performance (though not as good as the tegra 3)
PS overall the the snapdragon S4 will benchmark higher but that is mainly due to it’s really high I/O and Memory performance (much faster than the tegra 3