I would like to emulate the vertical spacing of tabular without using tabular. When the \parskip package is used, using \par leaves too much vertical space, so I thought I'd emulate it with use of a \newline:

Now, this seems to work just fine, most of the time. But am running into a Missing number, treated as zero which I suspect is related to using a \newline. Plus I recall something about using a \\ or \newline outside of a tabular or array type of environment being a bad thing.
So, my question is: Is using \\ or \newline a bad thing, and if so, why? What alternative ways can I emulate the vertical spacing of tabular when using the parskip package?
References
- Parskip: Suppressing parskip in some places suggest to adjust
parskip, but this is considered a "deadly sin" as per Too much whitespace before lists when changing the \parskip length
Code:
\documentclass{article}
\usepackage{parskip}
\newcommand{\ColumnA}[2][l]{\makebox[2.5em][#1]{#2}}%
\begin{document}
Output using \verb|tabular|:
\begin{tabular}{@{}ll}
abc & def \
uvw & xyz \
\end{tabular}
Using \verb|\par| leaves additional vertical space:
\ColumnA{abc} def \par
\ColumnA{uvw} xyz \par
\medskip
Emulating \verb|tabular|:
\ColumnA{abc} def \newline
\ColumnA{uvw} xyz \newline
\end{document}
\parskiplocally, just thought that that it was recommended int the linked questions to not do that. – Peter Grill May 06 '14 at 04:01