While I’m no expert in either XeLaTeX or LuaLaTeX, I’ve used both a bit, so I’ll try to write up some things that I’ve noticed in the “front-end” superficial user level.
... is the standard way of using fonts with both engines. I haven’t noticed remarkable differences in the outcome or font selection, but according to the comments to this question, there seem to be some.
This means, of course, that neither
fontenc should be used. Do make sure to save your .tex file in UTF-8.
Version 2.5 from 2013-03-13 seems to have improved XeLaTeX support a lot. For LuaLaTeX (and pdfLaTeX), protrusion and expansion are supported; for XeLaTeX it’s only protrusion. Since
microtype typically works great without further configuration, you can simply load it for any of the engines.
polyglossia only works with XeLaTeX. A minimal setup of
babel works with both engines (I think a recent update also included some improvements for XeLaTeX, is that right?), but the package description on CTAN still says: “Users of XeTeX are advised to use
polyglossia rather than
babel.” Hence, I’d follow that advice and use
babel with LuaLaTeX (and pdfLaTeX), but
polyglossia with XeLaTeX. That’s certainly the way it used to be.
On up-to-date systems, this package should not be necessary at all – that seems to be the verdict here on tex.sx. If anywhere, it should only be used with XeLaTeX; in fact, it produces an error message in LuaLaTeX (unless it’s loaded after
While there probably are some packages specifically tailored for XeLaTeX, I would assume there are (and will be) many more for LuaLaTeX, making use of the scripting language Lua being tightly tied into the engine. Two that I have used so far are Patrick’s
lua-check-hyphen, enabling you to easily check all hyphenations that occur in your document, and Mico’s
selnolig (announcement on meta), which automatically suppresses typographically undesirable ligatures for English and German, based on an extensive pattern list. (Check it out.)