Anecdotally, OCaml seems to often be faster than Haskell, though not necessarily materially so. More important though (in my opinion at least) is that it seems

Anecdotally, OCaml seems to often be faster than Haskell, though not necessarily materially so. More important though (in my opinion at least) is that it seems performance is more predictable in OCaml. High performance code in Haskell tends to rely on a combination of stream fusion, rewrite rules firing and judicious use of unboxing and bang patterns. I've heard it said that the OCaml compilers simplicity makes it far easier to know what code it's going to produce. Disclaimer: I'm a Haskell user, so it might just be that I'm more familiar with Haskell's warts.