I don't understand what makes user installs more convenient. Certainly, my preference would be for global all the time – I expect something that says it's going to "install" something to install it onto my computer, like any other installation program does. What is it that makes user installs more convenient in this situation?
You don't need 'sudo' access for user installs. This means that 'cabal install' works out of the box on every system, without needing admin/root privs (esp. important for students).
But students will be used to needing to configure this – in every other installation system out there they need to tell it to install in their user directory. Personally – I find it more convenient to have the "install" program do what it says it does! Install it! This would save confusion about old tools that do things globally, and not confuse students, because they're all already used to giving extra flags to make install not install things system wide. Bob