Any TPU case (like the Spigen) that protrudes past the screen will protect the screen from a flat drop to a flat surface, but only tempered glass will protect it from a drop to something that protrudes far enough to hit the screen (like a rock or even a high spot in a concrete sidewalk). The TPU cases have a good grip, but if you're the type who drops things, make or buy a lanyard, or use one of those coil things made for keys, and connect the phone to your belt.
(BTW, I use the iBlason case - it's similar to the Spigen. There a few manufacturers making similar cases.)