PPG is good stuff, pretty much the only thing we used in my old man's Austin-Healey restoration business. Hard to go wrong with anything from them.
As far as pros and cons, there are a few. A single stage will take more work to keep up, ie, buffing, waxing, etc in order to look good. That said, I think a properly cared for single stage looks better than a base/clear if both are in top form. The clears are usually harder, so they resist scratching better, but that's not always the case. The clear coat on my '04 Dodge SRT4 was ridiculously soft, I couldn't even use a car wash brush on it without marring it.
Typically, the clears will look better with low maintenance, but what you see it what you get. Anything under the clear is untouchable, so, if there are any imperfections, they're there to stay. And of course, I'm sure you've seen plenty of late model cars with the clear coats turning white, checking, or peeling. Shouldn't be an issue with PPG, but it does happen. And if it does, you're in for a repaint.
The single stage also makes repairs easier if there's damage down the road. You can work directly on the paint, to touch up scratches or dings. With base/clear, the clear gets in the way, making spot repairs more difficult. Usually you'll have to do an entire panel.
The one possibly exception to my single stage preference is metallic colors. These will have metal flakes in the paint (like B5 blue, for example). Reason being is this- you can't fix metallic paints anyway. Hang a run in the paint, you can't sand it out. You can sand it smooth, but you'll still see the "ghost" of the run in the concentration of metal flakes left behind. And you pretty much can't do spot repairs, since matching a metallic is nearly impossible. Air pressure, temperature, distance of the spray gun from the panel, all effect the concentration of metallic flakes, and as a result, the color. The same paint sprayed with the same set up on different days may not even match.
And you can over-buff metallic paints too. So, in that case, the "set it and forget it" base/clear makes some sense. That said, the clear coat on my B5 car (courtesy the previous owner and probably Maaco) is peeling off as we speak.