Although both WP Ticket and Software Issue Manager WordPress plugins are used to manage issues, there are major differences in terms of how these plugins are used in real life use cases.
WP Ticket is a customer support management system designed for multi-role support teams. Each issue is submitted in the form of a support ticket. Tickets are assigned to support agents. Agents are support team members who are tasked to resolve tickets to customer satisfaction. Tickets are not grouped under projects although you can group,tag and assign them to departments.
Software Issue Manager is a requirement management and analysis tool to support multi-role project teams. All issues are organized under projects. Projects can have versions. The main goal of Software Issue Manager is not to provide customer support but to develop qualified requests.
For example, a customer submits a support ticket using WP Ticket. Subsequently, a support agent is assigned to the ticket and qualifies the issue as a feature request (or defect) related to a product. If the issue is accepted by a product project manager, the manager creates the issue in Software Issue Manager and may decide to include the issue in a project. In that case, the issue is assigned to a developer who is tasked to resolve the issue. After the issue is resolved, the developer notifies the product manager. The manager asks the support team member to close the ticket and notify the customer.