Unfortunately, SML has no industrial users. At least, that I've heard of. It's a language that's used mostly in teaching and academic research. First ML I used was SML/NJ in my intro CS class, and haven't seen it since. Whereas OCaml has a many industrial users and is widely deployed. My favorite example is of course management layer for the Xen hypervisor[0][1], but there are more as well[2].
Adam Chlipala has a writeup[3] on comparing SML and OCaml that may be of interest to the discussion.
[0]: https://github.com/xapi-project
[1]: http://anil.recoil.org/papers/2010-icfp-xen.pdf