Being a vintage IWC guy myself, I'm partial to the fish. I like that there are multiple styles of fish. My cursory research indicates an outline fish was used on the stainless models and a more detailed fish employed on the gold models. (If I'm wrong about this, please correct me.)
The newer logo certainly fits the crown better, but I think it lacks a certain joie de vivre. It's merely a corporate logo. The fish on the other hand has style and verve.
Again, it's just me. Since I only own watches with fish I may be a bit biased. Of course if I ever get around to saving sufficient funds for a new Ingenieur, I'll love the crown -- and all the rest of the watch -- just the same.
Best always from the Great State of North Carolina,
Titanos