I'm using ST because I want to use the same editor for my code and data, and I rather frequently get 100mb-1gb textual data files, logs, tabular data in plaintext or json, etc - not big enough to require special tools to process (I mean, they're a small fraction of my RAM), so a text editor should allow to eyeball them and do some basic processing - edit a particular line, do interactive global regexp replacements to e.g. adjust the columns in a million-line file, etc.

I haven't tried Atom, but the Hydrogen plugin looks very interesting. How does it react to, say, being asked to do syntax highlight on a 100mb json?