A simple "adobe dtm end of life" Google search will give you plenty of articles and documents highlighting the benefits/improvements of switching to Launch, so I won't go into that here. But, as my search phrase suggests, the biggest benefit right now is long term viability.
DTM is going away, and you will soon (October?) lose the ability to create new properties or to manage rules or data elements. It will become a read only option. A short time later, the web interface will go away, and you will lose all visibility into your TMS configuration.
My recommendation is to begin the migration process now so you can address any issues long before getting locked out of DTM. And, if you're starting any new projects, start them in Launch.