AVR and PIC are much more powerful than ordinary 5 1, and they are used in many places, mainly in control. Stability and power consumption are much better than 5 1. AVR and PIC also have many series, which are produced by different companies. The price is higher than 5 1, and there is a lot of information to learn.
MSP430 is a product of TI, which is characterized by low power consumption and different series have different applications. Mainly used in portable devices, such as some portable medical devices.
ARM is a high-performance microprocessor. For example, smart phones are all ARM cores now, and CPU cores of electronic devices such as pad are all ARM cores, and there are many kinds of ARM cores. Details can be found in Baidu.
The words of DSP are mainly used for data processing. To put it bluntly, the computing power is very strong and the specificity is very strong. There are many kinds of DSP, and different ones have different uses. For example, TI's C2000 series is mainly used for high-speed control, servo motor control, power supply control and so on. C5000 series is mainly used for language processing, C6000 series is mainly used for high performance, and there are many such as multimedia signal processing.
If you are a beginner, first master 5 1 single chip microcomputer.