Import VS direct mode in Power BI

Capability	Import	DirectQuery
Size	Size limitation  Up to 1 GB per dataset	No limitation
Data Source	Combining Data from different sources	Cannot combine data from multiple sources
Performance	High-performance query engine	Depends on the data source response for each query
Data Change in the underlying data	Not Reflected. Required to do a Manual refresh in Power BI Desktop and republish the report or Schedule Refresh	Power BI caches the data for better performance. So, it is necessary to Refresh to ensure the latest data
Schedule Refresh	Maximum 8 schedules per day	Schedule often as every 15 mins
Power BI Gateway	Only required to get latest data from On-premise data sources	Must require to get data from On-premise data sources
Data Transformations	Supports all transformations	Supports many data transformations with some limitations
Data Modelling	No limitation	Some limitations
Built-in Date Hierarchy	Available	Not available
DAX expressions	Supports all DAX functions	Restricted to use complex DAX functions such as Time Intelligence functions.
Clustering	Available	Not available
Calculated Tables	Available	Not supported
Quick Insights	Available	Not available
Q&A	Available	Not available
Change Data Connectivity mode	Not possible to change Import to DirectQuery	Possible to change DirectQuery to Import