Hi @siva
DTUs are only available for Azure SQL Database and NOT for Azure SQL MI.
A typical answer would be, "it depends" ;-)
DTU is the "old" option to select a performance class which is a mixture of CPU, RAM, IOPS
vCore is the "new" option as many customers complained about DTUs - how is this calculated, and we cannot compare it to on-premise vCores...
So it is just your decision what you like (and understand) more than a real technical decision.
Start with a DTU database and test your application, then change to a vCore database and test your application, then make your decision...
If you just need a database, go with Azure SQL database; if you want to take more activities and have more options for configuring your database, then go with an MI.
And also take into consideration what Alberto said.