The most famous is Split archipelago, with islands like Hvar (also known as the St Tropez of Dalmatia) or Vis with beautiful riva and nearby spots for swimming, clubs and fancy restaurants.
The Dubrovnik area is more remote, either flight directly to Dubrovnik or a 2h bus from Split. Less islands in the area but one can also visit Montenegro for a few days while sailing in this area.
Zadar archipelago is more quiet with a lot of natural spectacular bays to anchor.