I like Michael Feather's quote https://twitter.com/mfeathers/status/29581296216

OO makes code understandable by encapsulating moving parts. FP makes code understandable by minimizing moving parts.

I think they can be used in a complementary manner. One area where functional thinking can be a benefit can be in code that is tested with a lot of mocks. Instead of having a bunch of objects that mutate state and that need to be mocked out, model that part of the program as a series of pure function transformations of data. It will be much easier to test and reason about.