There’s no single number describing “how much better” one processor is when compared to another. It all depends on application and when it comes to DAW usage it depends on buffer size. As you can see from Scott’s numbers, percentage varies from 70% (64 sample buffer) to 25% (256 sample buffer). You could except this value go down below 10% when using very large buffer, since in “pure CPU speed” 4770 is less than 10% faster than 3770.
And we haven’t even talked about audio hardware/drivers, which may have significant impact on the figures.
So your question is pointless. You should ask:
“What sort of performance increase have Cubase users with brand X model Y audio interface with sample buffer of Z seen between i3770 and i4770?”
Unfortunately I don’t think you’ll find many of those who have made this comparison. 