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Pro Free and open-source
Both AbiWord & Gnumeric are designed with low resource consumption in mind. As such they are great applications for older computers.
Over 30 languages are supported.
Pro Great import/export features
Pro Collaborative editing
Abiword is able to edit online collaborative documents.
Con AbiWord has a dated aesthetic
The interface hasn't had a facelift since it's inception in 1998.
Con Default format is only readable with Gnumeric
Gnumeric is able to read/write a lot of file formats including ODS, XLS, XLSX, but it's default .gnumeric format is only readable with Gnumeric.