There are subtle differences between how the meta package is installed and how tasks are installed, even if the meta package installs all task packages.
tasksel effectively runs apt install xubuntu-desktop^, that is, it installs all packages that have the xubuntu-desktop task field set. But it might also include some other tasks, and I don't remember. That said, both methods are somewhat crap as they do not mark packages properly as autoremovable.
Consider a package X depending on A or B. If you install it, it will install A as well. If you say install X B, it won't install X. That's the same effect for tasks, and may lead to slightly different choices.
There are subtle differences between how the meta package is installed and how tasks are installed, even if the meta package installs all task packages.
tasksel effectively runs apt install xubuntu-desktop^, that is, it installs all packages that have the xubuntu-desktop task field set. But it might also include some other tasks, and I don't remember. That said, both methods are somewhat crap as they do not mark packages properly as autoremovable.
Consider a package X depending on A or B. If you install it, it will install A as well. If you say install X B, it won't install X. That's the same effect for tasks, and may lead to slightly different choices.