I use Mail for personal and freelance while Outlook is required for my office work. Outlook does about a million things and that makes it much less user friendly for me. I'd stick with mail if you don't need all the integrations and extra bs Outlook provides. Using both on Sierra and haven't experienced any bugs with either to this point.
No difference of mail in Sierra compared to El Cap or even Yosemite as far as I can tell.
Even though I have Office 365, which comes with Outlook, I still prefer Mail. It is quick, almost bug free, handles multi mail accounts very nicely and consolidates them to a single inbox if you prefer it that way, has pretty handy features like smart mailboxes and Spotlight finds whatever you are searching instantly.
Right on, thanks for the insight. I've read there have been some issues with Gmail and the Mail app. I just wanted to make sure its a solid option to use.
We used to be able to reject an email and send back to sender...Apple decided that was not a good idea and deleted that feature in Apple Mail.....you paid for your Mac but Apple controls it.