Sonnet is more token effective then Haiku?

A catchy title, but in fact a question. I was trying to understand and optimize claude code for max token efficiency and found out an interesting thing:

• the subagents spawned by main agent on sonnet model, like opus models use tool search for mcp discovery, they are initialized lazily, which saves tokens.
• the haiku model subagants instead does not know how to use tool search and all mcps are loaded into context eagerly.

So, if a user for example has a big amount of mcps, and runs his lightweight tasks on haiku subagent - wouldn't he lose more quota than same task on sonnet agent? Did anyone try to measure the difference?