PHP:
Parsoid:
With PHP it is clear we have created a "red link" and not just that the image failed to load due to some intermittent network failure.
The counterpoint is that as a document model, the Parsoid version is much more consistent. If we removed the <img> tag we'd need to put alt, link and dimensions somewhere else, and clients would need to be updated (although VE already special-cases mw:Error images to make our CE rendering look more like the PHP output)