I switched from Sublime Text 3 to Atom recently. At the moment, Atom has exactly the same (and more) feature or plugins you can find for Sublime. There are no particular issues in passing from one to the other, so there are just 2 things to take into consideration:
ST3 is written in C++, so his main advantage is the speed and there's no comparison with Atom. Anyway the development of ST3 is almost stuck and most plugin developers and github users are moving on Atom. Moreover, Atom is moving forward faster in development: it is open source and the community is growing day after day, while ST3 is a closed single person stuff. These are primary importance things, which will make Atom far superior to ST3 and other editors in the near future.
I have no doubt, if the speed is not an issue, Atom is the best choice right now.