GRASS GIS vs ILWIS

GRASS GIS is a geospatial processing system for raster, vector, and other geographic data, including terrain, ecosystem, hydrology, data management, and imagery work. It contains more than 500 modules for processing and rendering geographic data, with tools for 3D voxel, temporal, image-processing, and spatial-statistics tasks alongside raster, terrain, hydrological, and vector analysis. Through GDAL-OGR, it supports nearly all common GIS file formats. Interfaces include a graphical user interface, command line, C API, Python, Jupyter Notebook, and WPS. GRASS integrates with QGIS and R and provides PostgreSQL and SQLite database interfaces; its official Addons repository has more than 300 extensions. It is free and open source under GPL (>=v2), with no warranty. The listed platforms include Linux, macOS, Windows, API, web, and self-hosted deployment. Prebuilt macOS applications are signed and notarized. Support includes a worldwide community as well as commercial consulting, training, and custom development.

ILWIS has no write-up on Specifiction yet; its figures are above.