I have said, and still say, that the Belkin Grip Candy Sheer is the BEST case for the iPhone 5. I have tried MANY similar TPU cases to try to find a better case, but most have failed. One case that needs honorable mention is the Magpul Field case. This case has amazed me. The fit, feel, and overall quality of this case is great! I will probably be switching back and forth between this and the Belkin now. I prefer the more simplistic design of the Belkin, but the Magpul is still a great looking case.
It's approximately the same thickness. I used to have a Speck CandyShell, and it was only ~1 mm thicker than the Belkin, but it was a noticeable millimeter. The Magpul is about the same thickness as the Speck CandyShell, because it is only ever so slightly thicker than the Belkin. All comparisons were done with each case lying facedown.