I am new to electronics. What is the difference between these two systems and what are the pros and cons?
Tonally, there is zero difference. The "Stealth" --aka "NC" for "no controls"-- means that there are no knobs for vol,bass,treb, and there is no battery compartment installed in the endpin area (the battery is in a conventional battery clip taped inside the guitar just like on aftermarket pickup systems). Some folks like the "pure acoustic" look; it is an aesthetic decision with no impact on what you hear.
FWIW, I have an RT that has this "ES-NC" in it (not by my choice but was built that way when I acquired it), and I'd go with the regular ES any day of the week. Some people are very much put off by the appearance of knobs and the endpin battery compartment. And for the life of my I cannot understand why as the knobs are very discrete and aesthetically unobtrusive, and the battery door is covered when playing with a strap. Not to mention with "NC" you lose all ability to adjust volume/tone on the fly live, and checking/changing the battery is a hassle (yeah, the ol' loosen strings and reach in the soundhole fun). On this last point, I think Taylor has designed the best 9v battery compartment on the market: immenently functional, yet all but invisible as it is integrated into the body contours so seamlessly. You can tell where my bias is
Hope that helps you a bit.
Edward