The "Page Title" is what will show up in the browser tab when the page is active – generally it makes sense for this to be the same as the Navigation Title, so that users don't get confused about what page they have open.
The optional SEO Title is what will appear in search engine results, if/when that URL ranks in response to a particular search query. It's totally fine to just allow the page title to be the SEO title, but you might be missing an opportunity to improve search rankings and click-through rates if you don't customize the SEO title.
Short answer: it's not automatically better for SEO if they're different, but fine-tuning the SEO title is a good idea since it plays a significant role in whether search engine users click through to your website from a search result or not.
Hope that helps 🙂
