Difference between sequential and state machine workflow in SharePoint

Sequential Workflow:

- It looks very simple like flow chart.

- Steps within the workflow execute sequentially, one after another in the particular order.

- A sequential workflow always progresses forward, never going back to a previous step.

- Sequential workflows are definitely much easier to design and maintain.

Statemachine Workflow:

- A sequential workflow executes in no particular order and these are based on events like OnTaskCreated, OnTaskDeleted etc.

- A sequential workflow moves from one state to another until the logic concludes the workflow has completed.

- Compared to Sequential workflows State machine workflows are difficult to design and maintain.

- In order to move to another event, the workflow needs to meet another state.

- The workflow doesn’t really have to end. It can stay in the same state for weeks.

Visual studio provides both Sequential workflow and State Machine workflow. But in SharePoint designer you can only make sequential workflows. 

You can also check disadvantages of SharePoint designer workflows.