It really doesn’t matter. I generally like to have a clean site and sometimes don’t have any sidebar at all. It does depend on the theme you select.
Check out Niche Site Project for example — just a search field & links in the sidebar.
Don’t make the mistake of giving the visitor too many distractions. It’s really not going to help if you have:
- a bunch of links to recent posts,
- most popular posts,
- 5 social media links,
- plus some affiliate ads in the sidebar.
The visitor will probably just be overwhelmed with all the choices.
I want people to focus on the content and chances are that someone arrived on your site because they Googled some term. They want the answer to their query, not other stuff.
If your site gets a lot of traffic (say 50k to 100k++), then it might be valuable to have some other distractions in the sidebar may pay off. But most of the time it’s better to have a clean looking site.