It will really come down to if you need the extra features of the Pro and are prepared to pay the extra price. Markus is designing the Pro to be as flexible as possible, which means all scaling/sync processing etc are on the FPGA. 5x takes a different approach and uses an older FPGA and custom hardware for the sync processing etc. Also we’re hoping the open source community gets behind the 5x and develops us some cool features like graphics filters etc, but I guess that’s to be seen.
I’ve found that 480p over SCART is somewhat darker than a straight VGA signal
There’s absolutely no reason why using composite sync rather than separate sync would do that. I suspect a cable/adapter problem if that’s what you’re seeing.
I understand that the 5X does not support RGsB – which is my preferred way to get 480p out of a PS2
That is correct.
Modern Vintage Gamer reported issues with PAL content on Amiga computers.
That I can’t tell you, I do have an Amiga so I’ll test it but I’ve not managed to secure one for myself yet, let alone any for resale!