Which are the key questions one has to ask to decide between Polyglossia and Babel for a LuaLaTeX project in 2019?
There has been a similar, more general question in 2012, but the packages have changed a lot in the meantime. Hence I open a new, more specific question.
Can we reduce it to a check list like
Use package A, if you need
- utf-8 characters
- right to left support
Use package B, if you need
- package foo, because A breaks foo
babel's new RTL support works better for LuaLaTeX than XeLaTeX, though I could be completely wrong.)
biblatex, but also some others like ctan.org/pkg/tracklang and packages using it
polyglossiahas the disadvantage that it does not expose language variants in a way that can be picked up easily by those packages. That means that there are some rough edges with dialect forms (
naustrian, ...). See for example tex.stackexchange.com/q/432347/35864. Most of those packages won't exactly break with
polyglossia, but they work better/smoother with
\defaultfontfeaturesis ignored altogether. This is a bug, already fixed on the repository. I'll upload the new version to CTAN very likely tomorrow.