Lab.js is a free and open-source software for designing and running experiments. On the other hand, Cognition also offers free services, but it includes premium features such as advanced analysis tools and priority support, which need subscription plans.
When it comes to flexibility, Lab.js offers fine-grained control over the experiment flow and stimulus presentation. Cognition, though, with its graphical user interface, allows for flexibility in designing studies without getting into the depths of code. This makes it ideal for researchers who prefer focusing on the experimental design more than the programming complexities.
Both Lab.js and Cognition have support systems: a user-friendly forum for Lab.js and a dedicated community page for Cognition. These platforms allow researchers to discuss issues, share ideas, and find solutions to common issues together.
In conclusion, while both Lab.js and Cognition are exceptional platforms for running online experiments, the choice between the two may depend on your specific needs, technical proficiency, and the complexity of your experimental design.