<p>I think this is a good question.</p>

<p>Sometimes such questions and their answers can be illuminating, as when someone asked <a href="https://stats.stackexchange.com/questions/141856/what-is-the-difference-between-various-kruskal-wallis-post-hoc-tests/141872#141872">What is the difference between various Kruskal-Wallis post-hoc tests?</a>, and, since I am the author of one of the four packages mentioned, I was able to provide some insight as to the statistical differences underlying the different results the OP was finding in my answer.</p>

<p>When might comparisons of output given by two or more pieces of software<sup>1</sup> be inappropriate? Do any of the following circumstances not fit our remit? What others might likewise not be a good fit?</p>

<ul>
<li><p>When the comparisons are shopping for software recommendations?</p></li>
<li><p>When the comparisons are about ease of use or implementation?</p></li>
<li><p>When the comparisons are not asking about <em>numerical</em> differences, but instead layout and scope of output? (E.g., Stata's <code>regress</code> presents sums of squares and degrees of freedom details that are not output by, for example a summary of R's <code>lm</code>.)</p></li>
</ul>

<p><sup>1</sup> Why does software come in "pieces?!"</p>
