Here’s how to guide (PDF) from NXP in choosing the right standard logic from various choices that fit your application.
Digital systems are running at faster speeds, operating at lower voltages, and they are becoming more highly integrated. Many functions can be integrated into FPGAs or ASICs, however, this does not mean that generic standard logic has gone away. Designers may choose to design with standard logic for the following reasons:
•The need for cheap, simple fixed functions with high speed and lower power consumption
•Space constraints requiring small packaging
•Bus driving capability
•Interfacing between mixed voltage systems
•Need for hot insertion capability
•Need for bus switching.