The ultimateGrblport:

• available for many32 bit processorsandcontrollers.
• hardware abstracted (HAL) architecture with processor specific drivers andshared core.
• openarchitecture supports3rd party driversandplugins,includinguser definedplugins.
• extended GCode support:tool changes,canned cycles, extra inputs and outputs, optionalparameter and expressionhandling,...
• networking(WiFi or ethernet) andSD cardoptions available for some controllers.WebUIoptions.
• Web Builderavailable for the most popular processors, no need to install a toolchain for creating the firmware.
• works with all mainstream GCode senders, some may requirecompatibility levelset to function properly.

Wiki,generalissues,discussionsandchangelogare found in thecore repository.