So recently GMail got an update where you can use it for all your email addresses. So for me I have my personal gmail, my junk yahoo and then my work exchange email. So instead of launching the gmail app, and then switching accounts within gmail, inbox combines all of them into one inbox.
There it organizes everything within categories like travel, finance, social, forums...etc. It ties into Google Now and all your other Google apps, so it's just a good overall experience. Instead of deleting emails or keeping them in your inbox, you can swipe right to mark it as done, where it doesn't delete it, it just moves it out of sight. Swipe left to snooze it, where it asks you when you want to be reminded of it, one option is "Someday", which is funny. Plus Google really hits it out the park with their new Material Design.