As I understand it, it kinda depends what you want to accomplish. Below is probably way over simplified, but how I understand the future landscape.
Rules API: If the logic can be handled via the Rules API, you can use it. But as the name suggests, this is only an API. Unless you want to code raw JSON, you need some kind of user interface. That’s what the Automation creator in the mobile app is. Its better than what we had in Classic app, but still can’t get multi layers deep with things like nested IF statements and such. More than likely they will keep the Automation creator in the mobile app pretty simple to make it easy for “normal” people. SmartThings is supposedly developing their own web based complex automation creator that works with the Rules API yet, but no word yet on if/when that will be released.
Endpoint SmartApps (the new version): The new concept of smartapps if basically you (or someone else) hosting your own logic and then subscribing to device updates via a REST API and sending commands via the SmartThings API. This lets you control whatever kind of automation you want, including with service outside of SmartThings, but since its externally hosted you either need to figure out your own hosting or pay someone to do that for you. It looks like these docs are a work in progress, but there is some info here: SmartApp Basics | SmartThings Developers
That’s simplified ! Seemed pretty detailed to me Jimmy thank you but all I want to do is recreate @cobra smartapps that control my fibaro rgbw
Smartapp
Rgbw set to come on at set time using one of the devices special options (light fade example)
If movement detected on external movement sensor, light comes on, current draw rises and switches on a v switch
Same v switch state is used to change rgbw light fade to white 100%
When movement times out from external movement sensor automatically, power draw goes below set amount
V switch switches off which triggers rgbw back to previous setting (light fade)
Has worked perfect for 3 years plus but I cannot recreate it in current automations
Basicaly the house front rotates colour under soffits when dark, if someone approaches the lighting changes to bright white, when they leave light fade resumes
I can trigger this smart app at anytime I want and using any special feature of the rgbw
I think the best thing to do for that device is find/pay someone to re-write the DTH (or maybe even Edge Driver) to expose all those custom capabilities properly in the new app and therefore the automation creator. Then you don’t have a need for a SmartApp specifically for it.
Pure speculation, but I think there is some development mileage yet. I am wondering if perhaps we will see the if ... then ... become an if ... then ... else ... as it seems like something you could almost get for free and that gives you an awful long of extra bangs without any real increase in complexity.
More comprehensive AND/OR logic in the conditions also gives you a lot of rewards but risks making the app too complicated. I wonder if that would be left to the Rules API.
Other than that I’d have thought it would be bells and whistles on what is there.
The Rules API will evolve to largely fill most of the gaps that webCoRE currently fills, and the replacements for bespoke SmartApps have been around for ages. Although they use different technology they will still be largely familiar in broad structure and I think potentially they are easier to work with and far more powerful.
I think there are still issues to resolve in terms of distribution and shared use of third party apps, and in general scaling up of the services. For example, I have heard tale of there being a limit of ten users in place for an app that needed to support thousands.