What are the main differences between PHPExcel and PhpSpreadsheet

Question

In project of PHPOffice there are two projects associated with spreadsheet file formats:

PHPExcel

PHPExcel is a library written in pure PHP and providing a set of classes that allow you to write to and read from different spreadsheet file formats, like Excel (BIFF) .xls, Excel 2007 (OfficeOpenXML) .xlsx, CSV, Libre/OpenOffice Calc .ods, Gnumeric, PDF, HTML, ... This project is built around Microsoft's OpenXML standard and PHP.

PhpSpreadsheets

PhpSpreadsheet is a library written in pure PHP and providing a set of classes that allow you to read from and to write to different spreadsheet file formats, like Excel and LibreOffice Calc.

What are the main differences between them?