This is a really broad question. The "most efficient" method depends on the nature of the data, the way the data is managed, and the nature of updates, and your experience and skill in ETL solutions. The source formats are somewhat trivial; it's what you need to do with them that matters.
Some folks have no problems taking 10 minutes to update 100k rows via a Portal API, while others are updating 100 million rows every 8 hours.
Once you add in different ways to acquire data, well, there are too many options beyond generic advice like "As efficiently as possible."
If you want specific advice, you'll need to provide more details on the process you are trying to optimize.
- V
