In R, data sources, intermediate results, and final results are all dataframes (slight simplification). With DuckDB, to have the same consistency you need every layer and step to be a database table, not a data frame, which is awkward for the standard R user and use case.
You can also use duckplyr as a drop in replacing for dplyr. Automatically fails over to dplyr for unsupported behavior, and for most operations is notably faster.
Data.Table is competitive with DuckDb in many cases, though as a DuckDB enthusiast I hate to admit this. :)
