TLDR: If you NEED dual video out and don't care about potential dual SDRAM, get the Analog IO. If not, get the Digital IO board. Currently the PSX core will work on single SDRAM but dual SDRAM might allow for additional features.
Common features between analog and standard IO:
- HDMI out via the DE10-nano
- Cooling fan
- System buttons and LEDs
- mini TOSLINK digital audio out
- User port for SNAC and mt32-pi
- Secondary SD card slot for computer cores only (don't you dare try to use it as extra game storage haha)
- JST headers to extend power, buttons, and LEDs
Analog IO unique features:
- Analog video output (Digital IO board can output analog video by using an HDMI to VGA adapter)
- Dual video out (analog + digital) (Digital IO can output either analog or digital video but not both)
- Analog audio output
Digital IO unique features:
- Power switch
- TOSLINK audio out
- ADC-In for audio input (NOT AUDIO OUT :)
- Allows for secondary SDRAM