Hardwired vs. Microprogrammed Control Unit 

Hardwired and microcode methods form two radically different approaches to control unit design. Each has advantages and disadvantages when performance and cost are compared.

Speed: Hardwired is the best approach when speed of operation is most important.
Flexibility of use: Microcoding provides considerable flexibility in implementing instruction sets and facilitates adding new instructions to existing machines.
Ease of prototyping: Microprogramming can be used for rapid prototyping of new designs or emulating several instruction sets.

It is worth mentioning that, in general, the Complex Instruction Set Computers (CISC), e.g. Intel family of processors (i.e. 8086, Pentium, etc.), use the microprogrammed control unit design approach. However, in general, the Reduced Instruction Set Computers (RISC), e.g. SUN SPARC processors, use the hardwired control unit design approach.

Improving Performance of Microprogrammed Control Unit

Fetching an instruction from the control store takes considerably longer than generating control signals using hardwired circuits. To improve performance of microprogrammed control unit, the following measures can be taken:

Use very fast memory for the control store
Use long microinstructions to simultaneously generate as many control signals as possible
Use prefetching: fetch the next microinstruction while the current one is being executed.