I have a hard time contrasting XeTeX and LuaTeX.
At the moment, I am using XeTeX almost exclusively, mainly because it uses UTF-8 as the native input encoding and because it supports TTF and OTF fonts.
However, the lack of support for pdftex’ microtyping is mildly annoying.
LuaTeX, on the other hand, does support this, as well as UTF-8 input and (rudimentary?) fontspec support.
So my question boils down to: Is there any advantage in using XeTeX over using LuaTeX? Has anybody used both and can compare them? In particular, LuaTeX sounds very experimental and unstable – but is this really the case?