I recommend you try it out with new Actions on Google Codelabs!
However, since it was released only a few weeks ago, many features we are used to from Dialogflow are missing. This could be a breakpoint for you if you are deciding what to use for your next Action.
I created comparison spreadsheet with a list of features and their availability. It will be updated when the feature availability changes or when there are new features for each platform.
If the feature is marked as unavailable, that doesn't mean it will stay that way. Actions Builder is still in active development and the table reflects the current state. It should help you to decide if you are starting a new project today, but features could change when you create the next one, so I recommend bookmarking the spreadsheet for future use :)
Thanks @afirstenberg for helping me with this!