Here are few major differences which made Craft 3 better than previous version Craft 2
- Plugin Store: We can search, try and buy plugins from Craft Control Panel which makes plugin use and installation process much easier and quick.
- Composer: Craft 3 is available as Composer Package which makes easy installation of Craft, plugins and updating Craft & plugins from Craft Control Panel.
- Multi-Site: Craft 2 localisation is Multi-Site feature in Craft 3.
- Image Editor: Its great feature is being added into Craft 3 which enables setting focal point, easy crop, rotate and flip.
There are other new feature link Assets Preview, Debug Toolbar, Element Queries etc.