The two major types of microcontroller architectures are Harvard Architecture and Von Neumann Architecture. Harvard architecture has two separate buses for instruction and data, allowing the CPU to access instructions and read/write data simultaneously. This is the major advantage of this type. On the other hand, Von Neumann's Architecture is based on consuming less memory by sharing a single bus for storing both program data and instruction data. Each architecture offers different advantages and disadvantages, allowing one to choose which one best suits their project's needs.