well for a start there is no i3 4670.
The difference between the two is minimal. They both have the same clockspeed (roughly) They are 1 generation apart, so in theory the I5 4670 will be approx 5-10% better than the I5 3470. And the other difference being the platform, the 4670 is an LGA1150 socket, and the I5 3470 is LGA1155