title: When to use imshow over pcolormesh?
body: <p>I often find myself needing to create heatmap-style visualizations in Python with matplotlib.  Matplotlib provides several functions which apparently do the same thing.  <code>pcolormesh</code> is recommended instead of <code>pcolor</code> but what is the difference (from a practical point of view as a data plotter) between <code>imshow</code> and <code>pcolormesh</code>?  What are the pros/cons of using one over the other?  In what scenarios would one or the other be a clear winner?</p>