Haskell has a steeper learning curve IMHO: monads are pervasive and are hard to understand, laziness isn't a common programming pattern and it adds complexity. I find type classes confusing as well, it's not always clear where things are defined.
I like that OCaml is close to the hardware, there are no complex abstractions. The module system makes it easy to program in the large (I love mli). If you avoid the more advanced features, it's a super simple language.
[0] I think most people just end up post-rationalizing whatever choice they have already invested in, I know I do :) With that in mind, maybe I as a mainly-Haskell dev should instead list some things I miss from OCaml: faster compile times, non-recursive `let` by default, polymorphic variants, labeled arguments
Ocaml is more practical, and less punishing (you can do IO without monads), but the most important diffrence is performance. Haskell is VERY hard to make predictable because its lazy. Ocaml is strict so general system performance is much easier to predict.
But they are sibling languages in my book, while i still prefer ocaml over haskell.
A big part of interacting with APIs (which I imagine Stategraph does) is just dealing with records, and working with records in Haskell is really annoying unless you bring in lenses which bring a lot of complexity.