The new SD450 has a 2.5 inch LCD compared to a 2.0 inch LCD on the SD400. However, the SD450 (2.5 inch) LCD has 115,000 pixels compared to the SD400 (2.0 inch) LCD which has 118,000 pixels.
Also, the SD450 is 10 grams heavier and very slightly bigger.
It doesn't seem much of an upgrade. It has a few extra shooting modes and thats it as far as I can see. I think I would still prefer the SD400. Can someone enlighten me? Why are canon going backwards in terms of pixels. Canon states there is no improvement to battery life.