Instantly cutting the power to a computer can possibly damage the hard drive or corrupt files causing data loss or requiring a complete reinstall. These problems exist with SSD's as well. If your system is in the process of writing or moving data and suddenly loses power, it's like a package falling off the FedEx truck. With computer systems, one missing "package" could cause a whole lot of problems.
Just hit Control+Eject and press return. It's that easy to shut down properly.