They are different cases, but both share a similar chassis.
The PC-60 has a removable motherboard tray with a single 80mm fan in the rear. The plus edition has a 120mm fan at the front, I believe both have an 80mm blowhole.
The PC-60 comes with a larger, more solid hard-drive rack compared to the PC-7.
The PC-7 is essentially a budget PC-60.