Their package size and pin definition are exactly the same, but the internal configuration of the STM32F103VCT6 is higher than that of the STM32F103V8T6, the STM32F103VCT6 Flash is 256k, while the STM32F103V8T6 is only 64k. The STM32F103VCT6 has 48k RAM, the STM32F103V8T6 has only 20k, the STM32F103VCT6 has 11 internal timers, the STM32F103V8T6 has only 7, the STM32F103VCT6 has 3 channels of A\/D conversion. STM32F103V8T6 has only 2 channels.