Google vs Yahoo over several years. A fable for scientists. Yahoo is worth countless billions of dollars less than Google, in spite of a big head start. The moral: methodological complications, always seen as “improvements”, have a price. The benefit of a more complex experiment is easy to see, while the increase in cost (difficulty) usually goes unremarked.
My usual comment on proposed research is that an easier experiment — often smaller, often less “well-controlled” — would be better. I seem to be the only person who says this, yet I say it all the time.