Basically more everything. 2x Cortex M33 cores with floating point, 520KB ram, more PIOs, bunch of secure boot stuff (I have mixed feelings about this), and can boot to a mode with risc-v cores instead of the M33s.
Keeping the same pin layout while upgrading to USB-C would have made more sense. USB-C is the future, seems odd to still be a Micro USB holdout in 2024.
The switch has got to happen at some point, and the Pico ecosystem is still young enough the change wouldn't be too disruptive.
I would rank SCART higher than the composite video RCA connector all of us had to settle for in the NTSC world. SCART was awesome in its day, being able to carry component video AND bidirectional equipment control signals. It was HDMI before HDMI.
I don't remember much problem with the connectivity with SCART. I do remember wasting many hours dealing with cheaply made cables that didn't even wire all the pins however.
Which come to think of it is now becoming an issue with USB-C cables. At least with SCART the connector could be easily opened for inspection, which became a habit of many an AV tech.
After mulling this I think they should have switched, since the original Pico will stay in production, and people can keep using it if they want a literal drop-in replacement. I wonder what the constituency was for staying with micro USB, i.e. that had existing designs that used the Pico but taxed its capabilities.