Wait what??? Exactly what is your question? Are you complaining that the i7 is faster than the i5? If so, it is probably because of Hyperthreading for the i7. I guess Premiere Pro is one of those milti-threaded programs that benefit from HT.
the i7-920 is twice as fast as the i5-750 yet they have almost exactly the same specs. Can someone explain this for me?
Core i7 920 has 2 major feature that the Core i5 750 dont have that can be causing the performance boost.
First feature is Hyper threading (HT), what this does is give the cpu better multi tasking abilities by having two threads per core. So the core i7 920 has 8 threads total. To the OS (like winodws 7 or XP) the extra threads look like additional cores. While it may not be as fast as having 8 true cores, HT gives the cpu an extra boost if the program can use it.
The second is triple channel memory. While it just like dual channel memory, triple channel uses 3 sticks of ram in 1 channel of memory. What this does is give the computer a wider bandwidth to access memory much faster.
As so ably pointed out above - The i7 has HT and triple channel memory, and therefore has a fairly significant advantage in overall throughput over an i5. As evidenced in the benchmarks the OP posted about.
These things do come at a price, and don't always 'matter' in the context of a given usage pattern, though. This is why it is highly useful to test a wide range of real applications and as well as synthetics. If you do that, then you know what the differences are, and whether they're applicable to your intended usage.
i.e. - If you spend a lot of time using Adobe Premiuere Pro, then it's probably worthwhile to buy an i7 instead of an i5. If you play Crysis while streaming Pandora? Not so much.