the SX120IS is a better all around camera. Great all around camera that has a better-for-birdies zoom and and since I have the same camera (but last years version) I can honestly tell you that the digital zoom works well at the lowest setting, making it a 20x zoom. I was pleasantly surprised by the high quality pic available with the digital zoom.
I have photographed thousands of birds with an SLR camera using 400mm (8x) and 500mm (10x) zoom and prime lenses and no matter how long your lens is, it ain't long enough! I set up a hummingbird flower garden a few years ago and was able to stay within 30 feet of the feeding birds using a 500mm lens and still could not fill the frame completely.
Using the little Canon camera on a tripod I can zoom to 20x and fill the frame with tiny birds. (20x is hard to hold steady, even with IS engaged a tripod helps tremendously)