Question: What is more efficient: Drill in OR subreport?

[diggy128]

Has anyone tested which is more efficient:

1. Drilling in by selecting fields from foreign tables and grouping OR
2. Inserting a subreport with the foreign table data?

eg.
case 1. Data source product.template with fields: name and code from product_variant_ids
case 2. Data source product.template with fields: name and subreport with data source product.product (filter on template id) and field code.