1. Architecture and Implementation: LaunchDarkly operates on a client-server architecture where the feature flag evaluation happens on the client-side, supporting extensive targeting and customized rollouts. On the other hand, Optimizely primarily uses server-side feature flag evaluation, allowing for real-time decision-making and advanced audience targeting, but with a fixed client library.

2. Experimentation Capabilities: Optimizely is known for its robust experimentation platform, offering A/B testing, multivariate testing, and server-side testing. It provides a range of statistical analyses, allowing businesses to optimize conversions and user experiences. LaunchDarkly, while offering basic A/B testing capabilities, focuses more on feature flagging and operational control.

3. SDK and Language Support: LaunchDarkly provides extensive SDK support across multiple programming languages and platforms, including web, mobile, and server-side frameworks. This allows developers to easily integrate feature flags within their existing codebases. Optimizely also offers SDKs, but with a narrower language and platform support, concentrating more on web and mobile experimentation.

4. Optimization and Personalization: Optimizely offers advanced personalization features, enabling businesses to create dynamic user experiences based on visitor attributes and behaviors. It allows for detailed audience segmentation and tailored messaging. In comparison, LaunchDarkly's focus is primarily on controlled rollouts and progressive deployments, rather than extensive personalization.

5. Collaboration and Team Management: Optimizely provides robust collaboration and team management tools, allowing multiple users to work together on experiments, manage access levels, and track changes. It also provides comprehensive reporting and analytics capabilities. LaunchDarkly, while offering basic collaboration features, doesn't have the same level of collaborative and project management functionalities.

6. Pricing and Flexibility: LaunchDarkly offers flexible pricing based on the number of feature flags, monthly active users, and integrations. It allows businesses to start small and scale as needed, making it suitable for both small startups and large enterprises. Optimizely, on the other hand, has a more structured pricing model based on feature sets and usage, which may be cost-prohibitive for smaller businesses.

In Summary, LaunchDarkly focuses on feature flagging and operational control with extensive SDK support, while Optimizely excels in experimentation capabilities, personalization, collaboration, and advanced analytics. Choosing between the two platforms depends on specific business requirements and priorities.