As you probably know, Outlook is overcrowded with features which could be nicely utilized, but this e-mail client hasn’t been updated for several years now. However, these two applications, even completely different as they are, can’t offer anything new or innovating at their current state.
This seems to be a forgotten area for some time, where Apple’s Mail and Microsoft’s Outlook dominated. One of the latest trends throughout OS X and iOS software development are all-capable e-mail clients.