I thought it was implied in the context, but the "more advanced" obviously meant "more advanced in terms of JSON support". Sorry if there was clarification needed.
What SQL Server 2016 will have next year seems to be more limited than what PostgreSQL 9.2 (by 2012) had. PostgreSQL at least had a native datatype ("json") to store text that syntactically validated JSON, while in SQL Server, 4 years later, you may have non-valid JSON data on a column expected to have JSON (unless you setup the validation as a constraint, which is prone to error and cannot be used in functions which expect or return JSON data anyway). Plus PostgreSQL had by 9.2 many functions to query JSON types in a very easy manner, while I don't see the same functionality coming to SQL Server 2016.
Regarding indexing, by 9.2's time you could use functional indexes to index arbitrary JSON paths (one index per path). In SQL Server you'd only be able to use computed (persisted) columns to index JSON paths, which seems to be a less elegant and less performing solution (more storage required) to the same problem.
So all in all, I honestly think that in terms of JSON support SQL Server 2016 will be less advanced than 2012's PostgreSQL 9.2, and definitely way less advanced than current's 9.4 or even more this year's 9.5. But that's, of course, only my opinion :)