When I'm doing development, I spend most of my time interacting with Atom. If I had to buy another pair of 16 GB DIMMs just for the sake of running it, I would. This is what I do professionally and I'm happy to throw a little RAM at something that makes my job more enjoyable and myself more productive.
I appreciate easy customization as much as any dev, but, in this case, I don't know if that's an advantage when as a result Atom doesn't do its primary task terribly well: stay open all day, let me type code.
I'm not suggesting Atom is better than Sublime, and there are definitely many cases where Sublime is better than Atom, particularly in terms of performance. I just think Atom gets more abuse than it should given how useful it is in general. Many of the complaints I see are more rooted in what they feel an app should do in the abstract (e.g. idle at under N megabytes of RAM) rather than actual issues that affect their use of the tool.
Presumably everything Electron based is using Irregexp under the hood, so I doubt that's a real competitive advantage.
The performance difference between Atom and Visual Studio Code is interesting, given that they're built on the same framework.