I got my first MacBook a little over a year ago and the first text editor I gravitated towards was Brackets. Don't get me wrong, Brackets definitely has some great features, but after a month or so of usage I noticed it was getting extremely slow.
I know my Macbook Air is not the most powerful of machines but I figured this had to be an issue with Brackets.
I asked my brother who works as a full-time web developer, and he recommended I try BBEdit.
When you go to the website, at first glance it appears as if there is only a paid version available. This is not the case! Simply click the 'download' link in the sidebar and you can use their FREE version for however long you want. Obviously you get more features if you pay for the pro version, but so far I've been very happy with how snappy this editor has been.
Try it out for youself! :)