When to Use Import Wizard versus Data Loader

See the answer below.

Need to prevent duplicates and when the Admin needs to choose whether to trigger Workflow rules (or not)

The Import Wizard and the Data Loader are both tools that are used in Salesforce to import data. However, there are certain situations where one tool is more appropriate to use than the other.

The Import Wizard is a web-based tool that is used to import data into standard and custom objects in Salesforce. It can be used to import up to 50,000 records at a time and is best suited for small to medium data sets. It is a good choice when you need to import data quickly and easily, without needing to write any code or perform any complex mapping. The Import Wizard is also useful when you only need to import data into one object at a time.

On the other hand, the Data Loader is a desktop application that can be used to import and export large amounts of data into Salesforce. It is best suited for large data sets and can be used to import up to 5 million records at a time. The Data Loader is a good choice when you need to perform complex data transformations or mapping, as it allows you to map fields between different objects and to perform complex transformations using formulas or scripts. Additionally, the Data Loader can be automated using the command-line interface, making it ideal for batch processing.

In summary, when you need to import a small to medium-sized data set into a single object, the Import Wizard is the best choice. When you need to import a large amount of data, or when you need to perform complex mapping or transformations, the Data Loader is the better choice.