Like you I gave this tons of thought. When ordering my car, I noticed that the 2015 model had an option to order it with carbon fiber splitter/rocker skirts, but I didn't want visible carbon fiber going against carbon flash options I had ordered. I wasn't too impressed with the design that GM offered for the amount of money they listed the option for. Plus the factory splitter/rocker skirts were on constraint which would further delay my build.
So with all those things going against my choice to stick with the factory option I started looking aftermarket. Even though I don't have my C7 yet as I just submitted my order a few weeks ago, I wanted to have the kit ready and waiting when the car arrived. With this car, I ordered the car with every option that I would otherwise modify if I hadn't order it in the first place as I want it to look and be as much from the factory as possible (I've heavily modified plenty of my cars in the past), but this would be one of the few option I didn't mind being aftermarket.
To me I wanted it to be an easy install using factory location to attach it without having to modify the car with added holes and what not. I wanted it to be an exact match to the other parts highlighted with carbon flash. I wanted it to look similar to the z06 ground effects as if it would of come from the factory as an option, but I didn't want it too extreme. With all this to consider, I started to look across the internet. I found plenty of options and though many of them are just as well made and priced, they were slowly removed from my list for one reason or another.
In the end I went with Weapon X Motorsports weapon7 splitter/rocker blades. They remind me of a mild version of the Z07 kit in all the right ways. They are fiberglass and painted to match the carbon flash (Carbon Fiber is an option). They were priced VERY reasonable (awesome deal in my eyes). As soon they come in I'm going to have them wrapped in some kind of clear protectant as I will for the car as well. This was also recommended to me from Weapon X Motorsports.
I look forward to getting them installing on the car as soon as my car is delivered, haha. I hope this has helped or just given you options to think about. Good luck on your future purchase.