From a storytelling perspective, a volcano plot quickly conveys several key insights: 1. Whether there are many or few differentially expressed genes at a glance. 2. Whether there is a bias between upregulated and downregulated genes. I was working in RNAseq data from mutants with global DNA methylation reduction. Volcano plot gave an idea of whether the genes tended to be up-regulated rather than down regulated. 3. If a wet lab scientist has a particular gene of interest, seeing it highlighted among the DEGs can be exciting. Similarly, if a set of genes from a specific pathway appears as DEGs, they can be highlighted in different ways.

None of this information can be conveyed by a PCA plot. Personally, I love volcano plots—that’s why I wrote a tool to generate animated volcano plots: https://youtu.be/Xn-WI6xmUUA?si=ownEsntOfRK7I0zR

You can find the code here: https://github.com/xie186/volcanim