Same gear, different name...

I was impressed by my friend's Canon Ixus 860IS during my Hong Kong trip, especially the 30 seconds timer and 28 mm wide angle. So I tried to buy the same camera, only found out that the exact same camera is called Canon PowerShot SD870IS. In fact, the updated version Canon PowerShot SD880IS has been released. So now I am in the process of researching to see which gear I should get: Canon PowerShot SD880IS (US$266.95 at amazon.com) or SD990IS (US$368.07 at amazon.com).