In a Boost Converter, where is most of the heat dissipated?
Hop on over to the TI page for this chip, and fire up the Webench.



That will tell you a lot about the power supply. Click on the Op Vals icon at the top, and it will list loads of useful variables.



Here you can see the power dissipation for the MOSFET, Diode and IC. It looks like the MOSFET dissipates the most power, and so will need the most heatsinking. Try it yourself, and put in the correct values for input and output voltages and output current that you'll be using.