Txurce
Deity
This. If you build say 5 envoys instead of 5 diplomats, you've gained enough production to more than offset a delayed factory.
The envoy is the more skippable tech in my experience. Workshops only strength is more production, but building emissaries instead helps offset that anyways. If I really want workshops for my empire, I just don't build diplo units for a while.
I often go with Statecraft, and gun for Industrialization as often as something else. Why? Ironclads. If the naval component is important to you, they are big. Also, it takes me a while to have enough paper to spit out diplomats. By then, I have enough factories/seaports to make the efficiency difference seem secondary.
Note that I am comparing apples to oranges, because that's what the tech forces you to do. I don't think you should decontextualize it to a strict envoy vs diplomat comparison at that stage in the game.