Steve Jobs has even personally said that the Nvidia benefits paired with C2D were a better all around Mac experience. The MBP 13" got the IGP because Apple is just going to sell the upgrade to 15" and 17" MBPs for all of the "real" pros who need a real GPU.
Why 13" MBP didn't stay with C2D + 320M combo if it provided better experience, even according to Steve? Apple could done what they did in 2010 and force people who care about the CPU to buy 15" and 17" MBPs. For some reason, Apple decided to go with Sandy Bridge in 13", even though it meant a loss in graphics performance. The most logical move is to do the same for MBA.
However, the IGP in the standard voltage SB used in the 13" MBP is running much faster than the IGP running in the low and ultra low voltage variants of SB. This comes down to a chip by chip basis. The MacBook and Mac mini can both handle standard voltage chips, so those would be next. Unless Apple makes a miracle happen and can run a std voltage SB CPU/IGP in the MBA it doesn't make sense... even then, it probably doesn't.
But from marketing standpoint, they are the one and the same. ULV and LV chips have the same Intel HD 3000 as the SV chips have. Apple doesn't tell you the clock speeds, or tell you that "hey, this is the same chip but it's actually much slower". In their site, it will be the same Intel HD 3000 as in MBPs. A consumer can't see any difference between them. The fraction of people who do some research and may find out that they are not equal is irrelevant.
You are one of the small minority that cares what CPU branding is in your consumer grade Mac. The vast majority just want it just works, and the MBA for the vast majority is going to be the fastest Mac they have ever used even with their "lowly" CPU, in your eyes.
And Sandy Bridge won't change that. It will work just like your current MBA does. Even if MBA had a Pentium in it, it would most likely feel as fast. However, even the dumbest customer can see that the MBA has C2D, which is probably something that his 5-year old Acer has, while all other laptops have iSomething. From a marketing standpoint, Sandy Bridge makes more sense than C2D, even if it was slower in real world. It's new and in consumers' eyes, new equals better.
Whatever... enjoy your thoughts. Pointless to debate with someone who cannot look at what Apple and the market has done and why...
It doesn't matter who you argue with, it is pointless because
none of us knows anything. You, just like we all, try to make step on Apple's boots and speak with Steve's mouth.