The VW, obviously. With most parts shared across 13 models and all models static for at least a year and usually longer. Plus VW has a good history of parts availability.
Tesla on the other hand is famous for both making minor changes to their vehicles pretty much continuously and a bad history of parts availability.
1M cars over 13 models mean you’ll have no parts at all. 10M identical cars means there’s massive third party supply. Parts are already cheaper than Toyota’s.
I have hosted the models (mostly regression and random forest) WV use to predict missing part availability at their dealership in 2018-2020 (considering sales in the area, average fabrication/delivery time, likeliness of the part having to be replaced, probably others).
I guarantee you that even if I don't like their car, their dealership will very likely have the part you need around the time you need it. It's not the only car-adjacent company that does something like this (Valeo for sure does it too, i worked with them also), but I'm pretty sure it's the only one who has an internal data scientist team working on it.
... What makes you think a VW ID.4 is obscure? I think it's usually the best-selling electric car in Europe. You see way more of those with recent (last few years) registrations in Dublin than Teslas.
Tesla on the other hand is famous for both making minor changes to their vehicles pretty much continuously and a bad history of parts availability.