The electric regional interconnection between countries is a major subject of the integrated generation and transmission planning. One of the purposes of this integration is to share large renewable generation sources between different bulk power systems. One alternative for the development of this integration is the development of HVDC-Grids based on the extension of the concept of multi-terminal DC converter stations to HVDC networks. This paper compares the regional integration between systems using HVDC-Grid or using conventional large HVAC systems. In both cases, an optimization planning processes is done. The methodology makes use of differential evolution optimization algorithms to search the optimal solution of the configuration of the HVDC-Grid or the large HVAC interconnection system. The benefits of a HVDC-Grid are shown on a test system that interconnects IEEE-RTS system and the IEEE 39 bus system in order to share two large generation sources.