Both hotels will satisfy your need to get away and recharge. Fully depends on what you want to do on your trip.

Ventana is about hibernating and hiking. Not much else to do...Carmel has some shopping and restaurants but is a solid 45 minutes to an hour away. Fine for day trip but I would say not feasible for dinner. I wouldn't do it for four days personally. The food on property would get very repetitive (and isn't that good) and not a lot of alternatives. But if you just want to sleep in, sit by the pool or light a fire depending on weather, and get on some trails...well Ventana is for you.

Napa will be more of a "home base" to get out to wineries and restaurants. Both will be open unless something changes for the worse. You will need to be more dilligent in making appointments but things will absolutely be open. My biggest worry would be availability of uber to be your designated driver to get you to yountville for better food. Even if that's not working well, plenty of good spots (and some decent shopping) that are walking distance in downtown St. Helena.

I'd give hard product edge to napa with better bathroom, newer build, balcony with fire pit, etc. Ventana has the wood burning fireplace inside and many suites have private hot tubs.

Views are to taste. Ventana in a forest with limited view of ocean. Napa is literally amongst the vines.

Napa definitely more compact with not much outside the rooms, restaurant, pool, and spa. Ventana is more sprawling and secluded.

You can't go wrong. as i started this out, depends on how to want to spend your time once you get there. Personally i'll go with napa.