I just finished a trip very similar to this one. I can't comment on Zandun, but I loved Todos Santos. The only problem with the city is that there's no truly luxury experience. The San Cristobal isn't a particularly great property. It's also pretty expensive for what it is. A few thoughts:
1) The property is quite far from the town, so you'll need a car.
2) The beach to which the property is adjacent is not swimmable.
3) The hot tubs were not cleaned properly.
4) The food was overpriced and not particularly good.
5) The rooms are not particularly good. There are a lot of rooms, the fixtures and architecture are cheap. There's no heating, which is important during the night around this time of year.
6) The bathrooms didn't feel particularly clean.
It was definitely a unique property in that it didn't feel like a chain, but it definitely didn't feel special in any way, and especially wasn't at a level worth bringing up on this sub-forum. I'd never go again.
They're building a new property called
https://www.paraderohotels.com/ in Todos Santos. I'll probably go back when it opens and try it out. Seems like it might be special.