Atheos IDE can be installed on your own webserver/webspace, which I like more than using an external SaaS, of which I don’t know if it will not perhaps close down one day or become expensive.
Atheos has almost everything you would expect from a programming editor, for example syntax highlighting, autocompletion and error warnings.
The advantage over desktop software is that you can work on your project from anywhere, provided there is Internet access and a web browser of course. The disadvantage could be seen in the fact that some desktop application have more features.
Unfortunately, Atheos does not have pre-made code sections and snippets. And I can’t find a way to create my own snippets. On the other hand, the aim and goal of the maintainers is to keep Atheos IDE slim and easy to use.