The following file has two different outputs in xelatex and PDFlatex. why?

My file is:

\documentclass[12pt]{article}
\begin{document}
\begin{quote}\renewcommand*\rmdefault{ppl}\normalfont\itshape
This text with xelatex should be italic. Is it Italic?
\end{quote}
\end{document}


Outputs:

And also:

• I get italic for either pdflatex and xelatex (and also luatex). In which one do you get upright text? How do you compile? – Phelype Oleinik Jan 15 '18 at 15:42
• @PhelypeOleinik you have an old version of latex, at least 2 years old then I assume? – David Carlisle Jan 15 '18 at 15:52
• @DavidCarlisle Running pdftex --version I get pdfTeX 3.14159265-2.6-1.40.16 (TeX Live 2015/Debian). According to my Ubuntu repository, it is the latest version available for my Ubuntu version (Ubuntu 16.04.3 LTS). Is it possible/safe to update to another version? Using the Zesty repositories, maybe? – Phelype Oleinik Jan 15 '18 at 16:01
• @PhelypeOleinik prior to 2015 xelatex (despite being a unicode engine) defaulted to 7-bit OT1 encoding, the same as latex, but since then xelatex and lualatex have changed to default to TU encoding. texlive 2016 and texlive 2017 have been out for ages and texlive 2018 is starting testing, but I don't know how that corresponds to the debian repo versions. texlive 2015 is rather old, especialy if you are using xetex or luatex which see more changes than pdftex – David Carlisle Jan 15 '18 at 16:24
• @DavidCarlisle Thanks for the clarification! I'll stick to the 2015 version for now, and wait for the next stable release of Ubuntu, that will be in a few months. I read somewhere that it is not recommended to upgrade packages to future releases (I don't know to what extent this is true for texlive). I mostly use pdfTeX, so I should be fine for the time being :) – Phelype Oleinik Jan 15 '18 at 16:44

LaTeX Font Warning: Font shape TU/ppl/m/n' undefined
(Font)              using TU/lmr/m/n' instead on input line 3.

LaTeX Font Warning: Font shape TU/ppl/m/it' undefined
(Font)              using TU/ppl/m/n' instead on input line 3.


There are no fd files set up for a font family called ppl in unicode (TU) encoding.

If you use fontspec and refer to a suitable opentype font family fd files are not required.

\documentclass[12pt]{article}
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}
\begin{document}
\begin{quote}\itshape
This text with xelatex should be italic. Is it Italic?
\end{quote}
\end{document}