The Llano A6-3420m has a more powerful integrated graphics core than the core i3-2350m. The Radeon HD 6520G is roughly close to a Radeon HD 5550 video card while the Intel HD 3000 is basically equal to the Radeon HD 5450.
In term of CPU processing power, the situation is flipped. The dual core i3-2350m is more powerful than the quad core A4-3420m. There really is no contest.
For gaming purposes, the Llano A4 would be the better choice since most games are dependent on the GPU rather than the CPU. But there are some games that are works better with a power CPU as well such as Civilization 5 and Skyrim.