Battery life is dependent on usage - I can get 4 days on my Pixel 2 if I don't use it much, or a few hours if I use it heavily, so whatever numbers you'll get from people are for the way they use their phones. The Pixel has a larger battery, and less bloatware, so the battery life will probably be a bit better. And you'll get an update for the Pixel every month (only until September 2019, but it will be current until then) and P and Q - and there will probably be LineageOS after that.