Canon's SD series of cameras are pretty much alike. They all produce the same "clearest, sharpest, nicely color-saturated images under all lighting conditions."
They all have the same engine and firmware. They only differ with megapixels, optical zoom and focal length. You just pick the one with the features you want.
Another difference, any SD camera with a 3.0 inch LCD will not have an optical viewfinder as there is not enough room for it.
Here is a comparison of the cameras you mentioned:
You mentioned "wide angle" but none of the cameras you mentioned have a wide angle lens.
I am planning to buy an ultra-compact digital camera and am told that for these, Canon is the way to go. I am having a hard time deciding between the SD850, SD790, and the SD890. I was initially pretty set on getting the 850 because it seemed to offer an overall complete package, but a recent read-through of reviews has made me consider the 790, which is said to take excellent pictures. The 890 also caught my eye with its wide angle lens, which would be helpful in capturing panoramic shots. The bottom-line is that I want the camera that has the capability to give the clearest, sharpest, nicely color-saturated images under all lighting conditions. Which one will do that for me?