Don’t use SmartThings.
No, seriously. It’s a very powerful system but not at all a robust one. As I’ve mentioned many times in the forums, my own requirement For mission critical automations is an MFOP (maintenance free operating period) of at least six months and preferably a year. SmartThings rarely lasts 10 days. Just in the last two weeks there have been at least two control outages. (See the status page.) And that’s not counting the scheduled outages of firmware updates which can be neither deferred nor denied and which, for whatever corporate reasons, don’t usually get posted to the status page.
There are a lot of things that I like smartthings for, but running mission critical robust schedules is not one of them.
That said, Of all the smartthings options the most reliable will be smartlighting running locally. But only some devices and only some smartlighting automations are eligible for local operation. And even those will be knocked off by the push updates.
See the following Thread for some more details:
How to: Planning for Outages
But again, it all comes down to your individual needs and preferences. Many people don’t even notice when smartthings goes off-line because they might be away from home or it might be a non-critical application.
In my case, I am quadriparetic and live most of my life in one of two rooms. I always notice, and home automation is much more than just a convenience for me. As I said, I do like smartthings for some use cases, but none for which robustness is a critical factor.