1. Key difference 1: Integration options - Optimizely Full Stack offers seamless integration with various popular tech stacks, including JavaScript, iOS, Android, Python, Ruby, and more. On the other hand, Unleash Hosted primarily focuses on serving feature flags to back-end services, making it a preferred choice for microservice architectures.
2. Key difference 2: Configuration management - Optimizely Full Stack provides a visual user interface that allows users to easily create and manage feature flags and experiments. It also offers advanced targeting and segmentation capabilities. In contrast, Unleash Hosted relies on a declarative configuration file, which needs to be manually managed and maintained.
3. Key difference 3: Experimentation capabilities - Optimizely Full Stack offers a comprehensive experimentation platform that allows users to run A/B tests and multivariate tests with ease. It also provides statistical significance and confidence level calculations. Unleash Hosted, on the other hand, primarily focuses on feature flag management and doesn't offer as extensive experimentation capabilities.
4. Key difference 4: Testing environments - Optimizely Full Stack enables users to create and manage multiple testing environments, allowing teams to deploy and test features independently. Unleash Hosted, however, primarily offers a single production environment and doesn't provide dedicated testing environments out-of-the-box.
5. Key difference 5: Data tracking and analysis - Optimizely Full Stack provides in-depth data tracking and analysis features, allowing users to monitor experiment performance, track key metrics, and derive actionable insights. Unleash Hosted, on the other hand, is more focused on serving feature flags and doesn't offer extensive data tracking and analysis capabilities.
6. Key difference 6: Enterprise-grade support and security - Optimizely Full Stack offers enterprise-grade support, including dedicated account management, SLA-backed service, and comprehensive documentation. It also ensures high levels of security, including data encryption, user access controls, and compliance with industry standards. Unleash Hosted, although reliable, may not provide the same level of dedicated support and security as Optimizely.

In summary, the key differences between Optimizely Full Stack and Unleash Hosted include the integration options, configuration management, experimentation capabilities, testing environments, data tracking and analysis features, and enterprise-grade support and security.