I can speak for Chrome's MCP which I have more experience.
replydevtools MCP will have access to more deep level fetures such as performance profiling, lighthouse and network requests in details (headers, auth, cookies...).
For example, I had success using chrome devtools mcp to debug frontend performance issues. The LLM captured and analyzed some nice traces and was able to isolate bottlenecks and unnecessary repaints and reflows.
Network request access is really helpful!
replyWhen having access to both backend and frontend, and then seeing what actual code is requesting and returning can really help with hunting bugs or doing basic QA.
I used the chrome MCP to profile a slow react page at my company, set a /goal and had it iterate until it achieved under 100ms responsiveness to actions.
replyClaude was able to identify the slowness and use various react tricks to fix the specific issues, all without my input.
I don’t think the playwright MCP can do this, unless I’m mistaken