When comparing Sparkfun SAMD21 Dev Breakout vs Teensy 3.2, the Slant community recommends Teensy 3.2 for most people. In the question“What are the best development boards?” Teensy 3.2 is ranked 2nd while Sparkfun SAMD21 Dev Breakout is ranked 4th. The most important reason people chose Teensy 3.2 is:
The Teensy board is easy to set-up and start using with Teensyduino. Even beginners will have no trouble doing it.
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Pros
Pro Cortex-M0 Processor
Run out of room for your program on your Arduino? You can use this.
Pro Arduino Compatible
Have Arduino shields you want to use? You can.
Pro Very easy to set up, even for beginners
The Teensy board is easy to set-up and start using with Teensyduino. Even beginners will have no trouble doing it.
Cons
Con Additional hardware is needed to connect to peripherals that are not 3.3V
This board only has 3.3V outputs, which is unsuitable to interact with several peripherals, which are either 5V or 10V. To connect to those, you need to get additional hardware.