We managed to get hold of side by side shots of the Samsung Exynos 4210, the system on chip that powers the Galaxy S2 (but not the Galaxy Tab 10.1), and the Apple A5 which can be found in the iPad 2 and almost certainly, the iPhone 5.
While that of the A5 was published earlier in March, it is the first time that the Exynos 4210 has appeared online. According to UBMTechinsights (which provided us with the shots), both the Exynos 4210 and the Apple A5 have roughly the same die size; 118 mm2 for the former and 120 mm2 for the latter. Both are far bigger than the Nvidia Tegra 2 which measures only 50 mm2.
A few points to note: Apple chose a rectangular design for the A5 (top die), which is fabbed by Samsung, while the Korean semiconductor firm, went for a square floor plan. Note how close to the edge the A5 connectors are, compared to the Exynos 4210 (ed: Chipworks published a block layout of the backside of the A5 chip here).
UBMTechinsights' chief analyst, Jason Abt, told ITProPortal.com "although we haven’t yet done a functional breakdown of the Samsung processor, one might conclude that both Samsung and Apple are packing some further functionality into their devices – perhaps for future use, or some other performance enhancements that aren’t immediately visible.”
Incidentally, the fact that Samsung is both one of Apple's closest partners and one of its staunchest rivals means that the Korean manufacturer is almost certainly aware of what Apple intends to do with any extra silicon area whose purpose is still shrouded in mystery.