Raspberry Pi Pico vs Arduino Nano

The two boards side by side, from the same board files BoardPilot uses to check your wiring.

Raspberry Pi PicoArduino Nano
ChipRP2040ATmega328P
ProcessorDual-core Arm Cortex-M0+ at 133 MHz, 264 KB SRAM, 2 MB flash8-bit AVR ATmega328P at 16 MHz, 2 KB SRAM, 32 KB flash, 1 KB EEPROM
Logic level3.3 V5 V
Header pins4330
GPIO pins2622
Analog inputs38
Default I2CSDA GP4, SCL GP5SDA A4, SCL A5
Default SPIMOSI GP19, MISO GP16, SCK GP18MOSI D11, MISO D12, SCK D13
5 V tolerant inputsnoyes
Flashing toolpicotool (UF2)avrdude
Arduino boardrp2040:rp2040:rpipicoarduino:avr:nano

Which one to pick?

Full pinout: Raspberry Pi Pico · Full pinout: Arduino Nano