The two biggest differences I noticed when I tried XeTeX was 1) the pdf files were much smaller than from pdflatex, and 2) I couldn't use microtype [1] with XeTeX.

I stuck with pdflatex to use microtype (which is awesome), and use pdfsizeopt [2] to crush the size of my pdfs.

(More details: LuaTeX also makes small pdfs and might be the way to go, but I haven't tried it much. The size advantage over pdflatex depends on the fonts in use. There is apparently microtype support for XeTeX in the works.)

[1] ftp://tug.ctan.org/pub/tex-archive/macros/latex/contrib/microtype/microtype.pdf

[2] http://code.google.com/p/pdfsizeopt/ and my notes on it: http://homepages.inf.ed.ac.uk/imurray2/compnotes/latex.html#...

False presupposition in the title: Context is not a Tex engine, it is a format, either for Pdftex (Context Mk2) or Luatex (either Context Mk4 or Mk2).

In the link the top rated comment makes the same observation.

I have used LaTex to write a few books. I usually use TexShop for OS X which uses XeTex so you get the unicode support, etc. Again, for the Mac, the Aquamacs version of Emacs has goot LaTex support built in, and is a good alternative to TexShop.

Your comment sounds like TeXShop only uses XeTeX, which is not true. TeXShop certainly has the option to use XeTeX, along with plain TeX, LaTeX, ConTeXt, and other variants. :-)

If anyone still needs convincing that these are superior to, say, Word: http://nitens.org/taraborelli/latex

http://www.kergis.com/en/kertex.html KerTeX is nice and small.

Not what I'd call 'New'---these have been around for a while and depending on you needs do quite well. I prefer XeTeX because as one of the answers said, 'fonts just work'.