CSV vs XLSX
CSV is plain tabular text; XLSX stores workbook structure, types, formulas and multiple sheets.
CSV
Use it when
Use CSV for interoperable flat data.
XLSX
Use it when
Use XLSX when workbook features or multiple sheets matter.
Decision rule
Choose the option that matches the real requirement, data size, maintainability needs and compatibility constraints. Avoid selecting a technique only because it is familiar.
Need clarity?Prefer the simpler option that expresses the business rule directly.
Verify before scaling
Run both approaches on a small known dataset if the difference affects financial, inventory or operational decisions. Equivalent-looking techniques can behave differently with duplicates, blanks, NULL values or version constraints.