In terms of built-in packages atom is way ahead of sublime. The themes and UI is also sleeker and nicer. But atom is slower as compared to Sublime and multi-place edit is also not there like in sublime.

I've used Atom for a while but I returned back to Sublime Text since Atom got slower when I opened multiple projects and files (Macbook Pro Late 2014).

But Atom still looks very promising and if they can optimize it somehow I'll definetely give a second chance to it.

Bottom line: Atom has all the advantages and disadvantages of open source software. It isn't quite as stable as Sublime, but has a top of community support and 3rd party packages.

I've used both, but my predilect it's Sublime, it has a faster star and doesn't crash.

Sometimes I use Atom for it's UI and it's packages, but besides that sublime it's more comfortable in my opinion.