for gaming 3470... but in heavy load tasks the i7's hyperthreading will help... IF its just for gaming the 3470 for sure but if you are editing video then the i7 is your choice...
If the i7 is cheaper, buy a CPU cooler and overclock it... if you do overclock you will get 3470 performance in gaming and i7 performance in heavy load tasks... The i5 also has lower power consumption so that may be a factor for you, but i doubt it...