Tried Atom for Mac right now. Opening a tiny (10k rows) csv file took multiple seconds, opening a larger (100k rows) csv put out a warning about potentially taking a lot of time and in a second simply crashed before loading it.
And why should you need that kind of machine to do text-editing?
If a text editor can't open a big file unless you are on a beast of a machine, it isn't a very good text editor.
When you regularly work on such files, Atom is the wrong tool for the job. For regular programming however, I'd argue it's far better than Sublime Text by now.