Arduino UNO
| Raspberry Pi
|
Microcontroller | Single Board Computer (SBC) |
Suitable for interfacing a fair number of sensors and actuators such as motors, LEDs etc., and to control them with precise (milli/microsecond) timing. | Possible to interface sensors and actuators, though not as good as Arduino in this. Precise timing is harder to achieve. |
Processes 8 bits at a time at @16 MHz. | Processes 32/64 bits at a time @ 700 MHz - 1.5 GHz (depending on model). |
Not suitable for intensive data processing, only basic networking (and that too with additional hardware). | Suitable for somewhat intensive data processing such as audio / videos / images, network-intensive applications (has built-in network hardware). |
Operates at 5V, fairly robust and doesn’t get spoilt that easily. | Operates at 3.3V (though it needs a 5V supply), not tolerant of 5V signals on pins and spoils easily if not careful. |
Typically does not run an operating system; only one program at a time. | Runs a full Linux OS; can be used like a normal computer. |
Other alternatives include ESP8266 / ESP32 which are more powerful than Arduino UNO, but less than Raspberry Pi. ESP8266 comes with built in WiFi support. ESP32 comes with WiFi as well as Bluetooth. Both are extremely popular for IoT applications and are unbelievably cheap (cheaper than even Arduino UNO)!
ARM Cortex M0+ / M3 / M4 based microcontrollers are popular too! There are ARM Cortex M based offerings from ST Microelectronics (STM32), Atmel (e.g. SAMD series), Freescale (Freedom series), etc which are all well supported too.
ESP8266/32 and some ARM Cortex M based offerings support MicroPython - https://micropython.org. MicroPython allows for interactive and easy programming without having to use C/C++, though it is not the best for applications requiring high performance / timeliness.