Don't hurt me
Gmail has swipe to archive and swipe to remind; those are the two killer Inbox features IMO and they're in Gmail. Inbox zero achieved.
I really liked Inbox but the search was subpar. The Inbox search results where you get "top results" and then "all results" was odd; it was duplicative every time. Just give me the emails, in chronological order, and I'll figure it out.
If I searched for an email, moved to another app, and went back to Inbox to reference the search results or the email again, the app reloaded, they were gone and I had to start over. Gmail has better retention: open a new app, go back to Gmail and your email is still there.
(Outlook on Android is the opposite, if you find an email you'll be stupidly stuck with it all day when you open the app, even if you navigated away or if you click on a new email notification in your notification bar: bam, back to the same email. Basic functionality errors that aggravate the user daily.)
However, Inbox wins with a better theme. Gmail on Android is unpleasantly white and bright red. Inbox also didn't have ads, did it? The ads in Gmail are cleverly unobtrusive but… they are ads.
Gmail on desktop was always slightly better than Inbox on desktop though, in my opinion. More options. Inbox on desktop seemed like a mobile app enlarged to desktop, which is what it was, right?