For the time being I'm targeting YAML and JSON, so satisfied with the feature set that Dhall is offering.

Easy to render output as either and bonus is if you know Python, Starlark is very similar

I checked it out, but it's not obvious to me how to target YAML or JSON using it. In contrast, the first use case the Dhall homepage is how to convert to YAML. There are other things Dhall makes obvious, like how to create a record type to target specific YAML/JSON constructs, with type-checking.

Also I prefer Dhall's evaluation model (all values are at collapsed at compile time into a single output value with no side effects) to Starlark's full-fledged 'runnable' model, e.g. with the 'print' function I can print out anything I like, including possibly secrets and passwords. This is impossible with Dhall.

That said, I do wish that Dhall had something closer to Starlark's syntax and better type inference :-)