In general, is it correct that SCART gives you the same image quality as VGA in the games that support the latter?
No, the standard Dreamcast SCART cable only supports 480i. I’ve never heard of someone coming up with a code breaker code to get around that limitation.
(And I imagine Codebreaker is a bit more convenient to use than reaching around behind the console to flip the switch on the Toro.)
Swapping discs and fiddling with AR codes is more convenient than flipping a switch? How do you figure that one?
For 480p games there’s no difference using AV1 or AV3 on the Dreamcast. For 480i and 240p games, AV1 is a better choice, so all round the Toro via SCART is the best option for OSSC.