Microsoft is working on cloud first approach which means that the SharePoint Server 2019 will have all the SharePoint online features. SharePoint online supports both Modern and Classic UI, where modern experience is shared on SharePoint server 2019 and classic ui experience is shared on SharePoint Server 2016.
Below is a list of difference between two Server versions:
|SharePoint Server 2019
|SharePoint Server 2016
|SharePoint home page
|A page with modern experience where you can easily find and access SharePoint sites within your organization.
|Class version shows the default SharePoint home page
|Lists and libraries
|Optimized list and library experience. Copy, move, share, sync commands on tool bar. Pin documents, create and customize views, can easily sort and filter content
|RSS Feed, Most Popular Items, Connect to Outlook, Connect to Office, Export to Excel and Bulk Checkin are few options listed in ribbon which are available in classic ui
|Modern Team sites wither modern home page which include modern news, site activity and page comment features
|You can use default classic page home page or can create one from available page templates or can also customize pagelayout.You can add custom or list view web parts on the page.
|Can use site themes and Modern UI pages for a custom look n feel. No customization through css and master pages
|Can use site themes, alternate css and master pages for custom branding.
|New Communication site template introduced in SharePoint 2019 which are similar in purpose of a publishing site but do not relay on site publishing feature.
|Communication portal is usually a SharePoint publishing site which require a master page and site publishing template.
|In modern site pages, you can only add modern ui web parts which can easily configure. They cover most of the modern web components. Old classic web parts cannot be added on modern pages
|A rich set of web pats is available which can be added on site pages and list views. Easily customizable and can add custom web parts using client side or server side web parts.
|Fast and responsive pages, support modern web parts
|Normal html pages which do not support modern web browsing, only support classic web parts.
|Not available in modern ui pages
|Modern Search Experience
|Class search experience