The difference is the black interior in the Enforcer and fans that includes. The Enforcer has a 200 mm red LED fan in the front and a 120 mm fan in the back. And the HAF 912 has only 2 x 120 mm fans, one in the front and one in the back (But the front 120 can be swapped for a single 200 mm fan.
In terms of internal layout, they're identical. But as I said the main difference is the look, black interior and the USB 3.0. It's your choice.