Most web interfaces have the classic sticky topbar + 2-3 columns layout (just like StackExchange).
Some but few websites use a different approach and, instead, have a collapsable sidebar (i.e. BitBucket):
While the first approach is surely the most familiar one to pretty much everyone who's ever used the Internet (including the 50+ generation) and I can imagine it will work better for them just because they're familiar with it, I don't quite understand why sticky top bars have become the Times New Roman of layouts and are almost a standard for any modern UI.
Sidebars allow you to:
so it feels like they should be preferred over top bars.
Do you know of any studies on this and what do you think it's best?