For MS Office (or any office productivity software) either one will be fine.
The Core i3-2350m would do better in Photoshop than the A6-3420m because Photoshop can use a lot of CPU processing power depending on what you intend to do. However, that is not to say the A6-3240m will be very slow, just not as fast (like driving 55MPH instead of 65MPH).
For games, the A6-3420m would be better because it has a more powerful integrated graphics core than what's found in the core i3-2350m. It like comparing a desktop Radeon HD 5550 to the Radeon HD 5450 graphic cards. Both are slow in comparison to higher end desktop video cards, but the HD 5550 is noticeably more powerful than the HD 5450 at low resolutions like 1366x768 which is the resolution of most inexpensive laptops.