I rarely, if ever, use Excel. But I find that Outlook in the browser wipes the floor with local Outlook, be it "OG" or "new" Outlook. Everything is much smoother, there are no window widgets crapping up (right now, the min / max / close and window title of my new outlook are black on a dark grey background - I'm using the windows dark theme). This holds even in Firefox on Linux – it's how I mostly interact with MS Office.

What's also fun to me is that the other day, I tried "opening in word" a .docx attachment I received in my locally-installed "new" outlook. It didn't even try to open my locally installed word on ask me anything. It uploaded the file to onedrive without asking and proceeded to launch word online to read it.