The difference would be huge, get the i7. The i5-4460 has 4 cores, but no Hyperthreads. In addition to having a faster clock speed, the i7 CPU you mention supports Hyperthreading and therefore doubles the cores to 8 that are available for Premiere Pro.
As Jim said get the I7. If they offer a i7 4790K rather than running at a base 3.6 GHz the "K" version runs at 4.0 GHz which will also cut your exporting time. If sometime in the future you need a little more speed it is very easy to overclock the "K" version and safely get even more speed out of it.
The performance difference with the 4790K is definitely worth the price difference. Most of the most common HD codecs will thread out ideally to 8 to 12 threads. Less than that and the performance starts to suffer.