What is the difference between these two components?
The PowerBoost 1000 Charger includes a boost converter that can handle up to 1000mA (1A) at 5.2V output:


  Solder in the USB connector and you can plug in any iPad, iPhone or iPod for 1000mA charge rate.


While the USB LiIon/LiPoly charger is only a battery charger, that means that you can only get whatever voltage the battery is at out of it (somewhere between 3.7~4.2V).

Most RPi setups are powered by 5V in its micro-USB connetor or at the header. So if you dont have a step-up converter, the first option is a more versatile solution.

If you are already powering your RPi directly with your battery and that works well for you, the second one will be enough. (However I dont think you can charge the battery while powering the RPi at the same time).

So if you need/want to charge your battery and power your RPi at the same time, back to the first option.


  With a built-in load-sharing battery charger circuit, you'll be able to keep your power-hungry project running even while recharging the battery! 


From: Adafruit PowerBoost 1000C overview.