Hi camerabeginner and welcome!
The main differences that I can see are that the es63 has more manual controls such as Aperture and Shutter Priority modes, and adjust Exposure Compensation.
The es55 is purely a fully automatic camera, leaving all exposure decisions up to the camera. There is certainly nothing wrong with that as most casual users never change settings anyway, even if their camera provides those options.
If the person who will be using it fits into the category of casual shooter, the less expensive camera may actually have a benefit. That benefit is that is has 10 megapixels (more than enough) whereas the es63 has 12.2 mp.
Both cameras have digital image stablization, which typically simply boost the ISO. When ISO is increased there is a great chance for noise in photos. Digital cameras with less megapixels may show less noise, which is desireable.
I don't know if their are similar cameras in that price range with OPTICAL image stabilization, but optical IS is more effective than digital IS.
Below are links to information about some of the terms used in my reply. If you have further questions, please let us know.
ISOhttp://www.digicamhelp.com/camera-features/advanced-settings/iso/Digital image noisehttp://www.digicamhelp.com/taking-photos/basic-techniques/noise-in-digital-images/Image stabilization (explains the difference between optical and digital IS).
http://www.digicamhelp.com/camera-features/shooting-modes/is-modes/