Ramps 1.6 is optimised and launched based on Ramps 1.4 & Ramps 1.5.
The Structure almost same as Ramps 1.5 , the difference is Ramps 1.6 have new 2pin connectors, which more simple and convenient to connect, also will not be burnt easily, what's more ,Ramps 1.6 have a good Heatsink above MOS tube in order to give a better function to heat dissipation .

Beside, the Power of Ramps 1.6 is more larger than Ramps 1.5, the largest power will be up to or 270W , and  Ramps 1.5 just can be up to 200W, or smaller than 200W.

Features:

• 4 layers PCB, optimize heat dissipation.
• It can be extended to LCD and other parts.
• There are heater and fan MOSFET outputs and 3 thermistor interfaces
• 5A additional security and component protection fusion
• Heated bed controls additional 11A fuses
•  Applied to 5 Pololu stepper drive board
•  Design of Pololu plate pin socket can be easily replaced or removed for future design
•  I2C and SPI pins are available for future expansion
•  Servo connectors are used for connecting limit stops, motors and light-emitting diodes. These connectors are gold-plated and have a rated current of 3A, which is very compact.
•  The LED will light when the heater has output
•  Choose 2 motors to connect to Z Prusa Mendell

Documents:

• Ramps wiki