All three options are great. Those high quality ACS rock guards appeal to people who prefer molded, 100% OEM looking pieces even if they're expensive, and there's absolutely nothing wrong with that.
The ZL1 Addons (or RPI) mudflaps are simple and cheap, whereas my Rokblokz units have several advantages over them: thicker material, wider profile both front and rear, better mounting hardware (big bolts for the rear, non-marring front attachment), full coverage across 305 width rear tires which also protects the rear diffuser, lines that are a perfect match with the pre-refresh Camaro design, to name a few, at the same price as other mudflaps. Then again, these don't look as fancy as molded, glossy ABS pieces.
Good thing we have options here as well
In terms of vendors, I've had much success with GMPartsDirect and RockAuto for OEM stuff, then Phastek, Wildhammer, RPI, Gen5DIY, C7 Carbon, Next-Gen Speed and a few others for aftermarket parts.