The Teensy is a breadboard-friendly development board with loads of features in a, well, teensy package. Tons of functionalities is jammed into a 1.4 x 0.7 inch board.
Seeeduino XIAO carries the powerful CPU-ARMG; Cortex & -MO (SAMD21G18), which is a low power Arduino Microcontroller, on the other hand, this small board has a good processing performance, and needs less energy. In addition to the powerful CPU, the Seeeduino XIAO excels in many other functions. It has 14 GPIO PINs, which can be used for 11 analog PINs, 11 digital PINs, 1 I2C interface, 1 UART interface and 1 SPI interface.
This is the first Arduino board created in collaboration with Raspberry Pi. The Arduino Nano RP2040 Connect is based on the Raspberry Pi RP2040 chip and is the first card to combine this microcontroller together with additional sensors and wireless connectivity. This board has the Arduino Nano format and the same interfaces: USB, SPI, I2C, 12S, PIO, UART, PWM, digital / analog pins, but it has many more features. The Microcontroller is the Raspberry Pi RP2040 , a dual-core ARM Cortex MO + with a frequency of 133MHz, 264Kb of SRAM memory and 2Mb Flash.