You're right. I got 13'' MBA first but found out that I really wanted it to be a bit smaller so I got 11'' MBA later.
Basically I just cannot find a solid reason to get an iPhone. Almost everything I can think of I am better off doing on either iMac, MBA, or iPad 2 instead on an iPhone. Interestingly, although I could not identify one solid reason to get an iPhone, I have a feeling that I will soon succumb to the temptation get an iPhone anyway just so I will have a complete lineup of Apple devices. Oh well..
Sell one of the MBA for an iPhone 4S