They tend to be more durable than fiberglass. Other than that, the look just depends on what you want. Some kits are more radical than others. You can mix and match as well, like using a wings west front with stillen side skirts and rear if you want. Just find the look you like and go with it. Don't worry about what other people say.
You'll need to check the rear valence you decide to use. Many of them go on over the stock rear. So you'd need the stock rear already in place. I'd also go with door fillers if you get side skirts. They tend to smooth out the lines.
