Tasks and Events versus Activities with Objects Report Types

Tasks and Events Report Type

The "Task and Events" report type returns Activities across multiple objects (such as Cases, Accounts, Contacts, Leads, Campaigns, and Opportunities).
 

As a result, these reports can be more susceptible to time outs as they typically query several objects

Activities with Object/Object with Activities Report Types

You can improve activity report performance by using the other report types more specific to a single object, like the "Activities with Leads" report type.
 

Though this limits the Activities in the report to those related to the selected object, the performance on these reports is much faster since they are querying fewer objects.
 

Note: When creating reports using the "Activities with Object" report type, custom information from the object will not be available. As an alternative, Create a Custom Report Type for the object and add Activities as the secondary object.