FYI, connect supports a shorthand syntax for method binding. Just pass an object full of action creators instead of a mapDispatch function, and you will get those action creators bound up, as props. For example:

const actions = {onDeleteFlashMessage : deleteFlashMessage});
export default connect(null, actions)(MyComponent);

Overall, I prefer to define separate action creators outside of mapDispatch, and bind them using the shorthand syntax. That also makes the functions more reusable and testable.

I talk about this a bit in my blog post on Idiomatic Redux: Why Use Action Creators?.

I use code like in your second example. I don't really have any strong reasons. Sure, functional programming is cool but bindActionCreators seems unnecessary to me; and sometimes the action isn't as straight forward as passing in the parameter (id in your example).

But also, I write in an ES6 style because it's slightly more compact:

 const mapDispatchToProps = dispatch => ({
     onDeleteFlashMessage: id => dispatch(deleteFlashMessage(id))
 })