I am buying a Macbook Air and would like to know about the difference between the i5 and the i7 option. The i7 is only 100mhz faster and has 1mb of extra cache on the CPU. Does that small difference make a big difference to performance? Or is it so small that its not really worth the AU$100 extra?
AnandTech did a report comparing the two options and came to the conclusion that there isn't really a noticeable difference. Just 7-12% improvement on certain benchmark tests.
Below are the figures they got for reference.
I see you are in Australia. There was a recent article published by PC World Australia that goes into some detail on the differences between these processors at a technical level.
The i7 has a larger on-chip cache than the i5 (4 MB instead of 3 MB). A larger cache can speed up intensive operations like video encoding.
MacBook Air 2011 i5 vs. i7
Mac Crazy published an article specifically directed at answering your question with relation to the MacBook Air it was titled, "MacBook Air 2011 i5 vs i7 – Is the upgrade worth it?".
They include this table detailing the two i5 and single i7 CPUs used in the mid-2011 MacBook Air models.
There bottom line was this,
I would argue that people who are that speed sensitive would probably do better to buy a MacBook Pro.
Air vs. Your Current Machine
I am a designer who makes extensive use of Photoshop and I have been very happy with my recent purchase of a MacBook Air i5. The MacBook Air easily beats my MacBook Pro. Here's a video from the article showing a MacBook Air i5 beating a 2010 MacBook Pro 15″ Core 2 Duo 2.66 GHz: