The 1.2Ghz Exynos and the 1.5Ghz Snapdragon trade punches in benchmarks(some people will tell you the Exynos is just plain better but that is false) depending on what is being tested. The Mali 400 gpu(found on the Exynos is more powerful than the Adreno 220 that is paired with the Snapdragon.
The Galaxy Nexus is the superior phone between it and the GSII. The OMAP 4 rivals the Exynos in performance, the screen is significantly better, Near Field Communication support, better camera, vanilla Android with no bloatware(no stuff running in the background to slow you down), not only is it the first with Android 4.0.1, but it will be the first to get updates beyond that. It is too early to tell on the Galaxy Nexus GPU because no benchmarks have ever been run on a 384Mhz PowerVR SGX540 but it's very possible that it is faster than the Mali 400.