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I have a 1965 250 that I am restomoding. Any advantage switching to 12v vs just doing Electronic 6v ignition?

Nothing wrong with staying with 6V, as long as you can get bulbs, batteries, horns etc.
The factory CDI is not 6V, more like 200V-300V, self-generated not needing a battery.
You could get a battery powered CDI or other elec ign I guess.

Jorden,

the factory CDI comes from the later wide case models, was not available in 1965. It's stator plate (w/coils also for CDI power) does not fit into the narrow case engine without modifictions (i have never tried this). And it will be very difficult or even impossible to push the CDI power cable into the feedthrough nut, where the alternator cable already fills the entire orifice.
If one wants to improve the points ignition, he can install an electronic "amplifier" i. e. from Gammatronix: https://gammatronixltd.com/epages/bae94c71-c5b6-4572-89a1-e89006e78fbe.sf/en_GB/?ObjectPath=/Shops/bae94c71-c5b6-4572-89a1-e89006e78fbe/Products/%22POWER-DRIVER%206v%22. This is inexpensive and improves spark power. If you want to replace the mechanical points by an electronic trigger pickup, the Sachse MHP system should be chosen: https://www.elektronik-sachse.de/shopsystem-3/en/digital-ignition-zdg-3-10-6v-for-ducati-250-450.html.
A CDI is in my opinion not the best solution for a four stroke engine, which was proven by the Motoplat CDI mounted on later widecase singles.

cheers Hans

From my simple understanding (as a mechanical engineer), 12v means that less current flow is needed for any given power e.g. headlamp bulb so less power loss in wires etc.
My recently rebuilt 175 is running standard points ignition with the original generator. I’ve fitted an Electrex reg-rec set to 12v.
Ian

Hi Hans,
You are correct, in 1965 it is narrowcase. I'm not a great historian is my excuse.

Regarding the thickness of the CDI type alternator cable, I get around this by a rough and ready method:
using a multi core cable made for 3 phase industrial equipment.
The outer insulation is not so thick as the original stuff fitted to Ducatis, but the copper conductors are adequate.
It may raise eyebrows, but I'm willing to chance that the thinner insulation will be OK. Failure here is not likely to kill me.

Regarding your dislike of CDI on 4 strokes, is that because it doesn't have a resonant effect with a longer spark duration?
Nevertheless, it seems to work fine (when it works!) even on big 450 cylinders. There are probably millions of Asian 4 strokes running CDI ignitions.
I'm off Motoplat too, but it's because they always seem to fail eventually, then they are the devil to fix (potted windings and diodes in the stator!).
That's why I home made an alternative without the damned resin-encapsulation.

Thank you for all the replies. I think I will go with the Sachse 6v ignition upgrade and keep it 6 volt system. No problems finding bulbs and fuses etc.