Best data upload formats
Generally, CSVs are the smallest file size for non-binary (text) data. XML adds a great deal of xml codes that bloat the file size. So CSVs tend to import faster. But XML importers can handle exception cases, etc., with more complexity.

In my career, I've worked with instrument imports at four different kinds of laboratories. Where there was no direct LIMS (Laboratory Information Management System)-to-instrument interface system in place, we found that delimited text files are the fastest to write working import scripts around. 

CSV is a comma-delimited text file. If your input data will include commas, then using a different delimiter may make more sense, like a pipe character for example: | A CSV file or pipe-delimited file generally follows the rule that each row/line of text from column 1 to the end-of-line carriage return represents one row of sample data in your database. Then within that row, each column of data in your database is separated from other columns by your delimiter character(s), which could be commas or pipes or anything you want to use.

Text files are great as long as the data is consistent over time.