I guess for all intents and purposes, the 3770 is more POWERFUL, but only in certain circumstances, the only difference between the i5 and i7 is slight clock and cache changes, but mainly the HyperThreading, which will make next to no difference in gaming, until multi threaded games start to come out.
Depending on how much you want to stretch your budget you can go for a 3770 if you do a lot of engineering and enconding and in that case, then 3770 will benefit you quite a bit. But the 3470 can handle it fine as well, you might see a 10%-20% difference in mulit threaded apps with an i7. So it's up to you to decide how much heavily threaded tasks you do, and is it worth paying $100 dollars extra to benefit yourself in those.
If you were to go for the i5 I'd recommend getting a 3570, for an extra 200MHz, which is just a small boost, but every little helps, for a small price change.