Could someone summarize features which are (1) common and (2) different for the
polyglossia packages? I know that
babel 3.8 (current version) fails to run for some languages (eg, Russian) under LuaLaTeX and XeLaTeX (at least it was so 2 years ago). What will be the future of the
polyglossia package if
babel 3.9 (which is now
babel-alpha) will manage to work with XeLaTeX? Will be any sense to use
polyglossia as a replacement of
babel in that case?
UPDATE: I am sorry for mixing several questions in one post. Main question was about differences between
babel. For example,
polyglossia has options specific to some languages.