Wireless QI which one?

[fascinated]

I'm looking at a few of the wireless qi addons to use with my standard S4 back cover.

Which of these works the best and doesn't make the cover bulge out?

Amazon.com: Smart Tech Qi Wireless Charger Wireless Charging Receiver For Samsung Galaxy S4: Cell Phones & Accessories

Amazon.com: Qi Standard Wireless charging Receiver for SAMSUNG Galaxy S4: Cell Phones & Accessories