1. Storage and Query Execution: DuckDB is an in-memory analytical database that focuses on fast query execution by utilizing vectorized query execution and a columnar storage format. It is optimized for data analysis workloads with complex queries and joins. On the other hand, JSONlite is a lightweight document-oriented database that stores data in a JSON format and provides functionality for querying JSON data.

2. Database Schema: DuckDB follows a traditional relational database model with support for tables, views, and SQL queries. It allows you to define and enforce schema constraints such as data types, primary keys, and foreign keys. JSONlite, on the other hand, does not enforce a strict schema and allows for flexible document storage. Each JSON document can have a different structure and different fields.

3. Data Representation: DuckDB stores data in a compressed columnar format, which provides efficient storage and retrieval for analytical workloads. It supports various data types, including numerical, textual, and temporal data. JSONlite stores data in a JSON format, which is a hierarchical data structure that allows nesting and storing complex data types such as arrays and objects.

4. Query Language: DuckDB supports SQL as its query language, allowing for powerful and expressive queries. It provides various SQL features such as aggregations, window functions, and subqueries. JSONlite provides a simple query API for querying JSON data. It allows you to perform basic operations like selecting fields, filtering documents, and sorting results.

5. Concurrency and Scalability: DuckDB is designed for single-node deployments and does not provide built-in support for distributed or parallel processing. It is optimized for efficient processing of a single query at a time. JSONlite is also designed for single-node deployments but can handle concurrent requests and can scale horizontally by sharding data across multiple instances.

6. Data Integration: DuckDB allows for seamless integration with other data analysis tools and frameworks like Python, R, and Pandas. It provides connectors and APIs that enable easy data exchange and interoperability. JSONlite, being a lightweight database, does not provide extensive integration capabilities but can easily interact with JSON-based systems and libraries.

In Summary, DuckDB is an in-memory analytical database with a focus on fast query execution and efficient storage, while JSONlite is a lightweight document-oriented database that provides flexibility in data storage and querying.