Elegant fractions in one line

Question

What solution do you think is more elegant for a simple fraction that should be displayed in just one line?

My examples are

1. $x_F \equiv \frac{p_z}{p^{\rm MAX}_{z}} = \frac{p_z}{\sqrt{s}/2}$
2. $x_F \equiv \frac{p_z}{p^{\rm MAX}_{z}} = \frac{p_z}{\sfrac{\sqrt{s}}{2}}$
3. $x_F \equiv \frac{p_z}{p^{\rm MAX}_{z}} = \frac{p_z}{^\sqrt{s}/_2}$

This generates the following (using the xfrac package).

I don't like 2, but I also think that 3 is not very elegant.

Answer 1

It is nearly always best to use the slashed form for fractions in the text:

\documentclass{article}

\begin{document}
\( x_F \equiv p_z^{}/p^{\mathrm{MAX}}_z = p_z/(\sqrt{s}/2) = 2p_z/\sqrt s \)
\end{document}

Note that I have added brackets to the second fraction.

Answer 2

There is also nicefrac package which provides \nicefrac{<Nr>}{<Dr>}:

\documentclass{article}
\usepackage{nicefrac}

\begin{document}
\( x_F \equiv \nicefrac{p_z}{p^{\mathrm{MAX}}_z} = \nicefrac{p_z}{(\nicefrac{\sqrt{s}}{2})} = \nicefrac{2p_z}{\sqrt s} \)

\vspace{.5cm}        %% Andrew's method for comparison purpose.
\( x_F \equiv p_z^{}/p^{\mathrm{MAX}}_z = p_z/(\sqrt{s}/2) = 2p_z/\sqrt s \)
\end{document}