Since the drivetrain exists to ensure you can shift between gears, improving the quality of those gear changes is an excellent place to focus on upgrades. With the new RED, SRAM has focused on improving the speed of the front shifting. By narrowing the front derailleur cage and reshaping the outer plate, they have made for quicker engagement and more contact with the chain during shifts
To address any noise from the new tighter tolerances, they have also improved their auto-trim and YAW functions by having the front and rear derailleurs communicate to make sure that even in major cross-chain positions, the front derailleur is aligned with the chain's direction—you can run your big front chainring and your largest rear cog without the slightest hint of chain noise. What a time to be alive!!