There isn't a game out there that you can't play with 1.2. .3 isn't going to make any difference. If that's what you want by all means get it, but if no one was told the specs you would never notice the difference.
Yes, today there is no game or software that can push exynos 1.2GHz to its limits, but if someone is buying this phone for next 2 years, there will be games available by then which would need higher speed. 0.3GHz, even if its a small number, is still a 25% boost in the clock speed, which is significant, and can keep this phone powerful with future games for little longer. I understand there would always be next bigger thing, but its not about next big phone, its about keeping my current phone big for little longer in a highly fast moving mobile hardware industry.