Pdf is much less useful.
I also cannot contain formulas. Only data.
If your process can read and write to Excel it is a much better defined format.
PDF is the canonical way to preserve formatting where that is important. A court document electronically filed in PDF in 1999 is identically rendered today. The source .doc or WordPerfect file is not.
After data collection (or during), then output can be made in any format you would like. In addition to what anybody would want to print right off the spreadsheet.
The XLS(X) file forms a database and UI, contains a copy of the input macros and output macros, and you save the whole thing every time which backs it all up (over and over and over again) in a form that anybody can open anywhere with a PC that only has Windows & Office. And whoever opens it will be right up to speed as good as they can be with whatever abilities they have using Excel alone.