Will something stock android like pixel have better battery life than Samsung phones?

Not necessarily. Android OS and the screen are usually the largest battery consumers. (Followed by phone idle, if you chose a carrier that doesn't have a strong signal where you are.) About the only difference may be Samsung's AMOLED screen, if the other phone doesn't have one and you like light-colored wallpaper. AMOLED screens use more power displaying lighter colors. But aside from that, the amount of current used depends on a lot more - that's part of Android - and has very little to do with the manufacturer. (Of course a phone with a larger battery will last longer between charges. But, again, that has nothing to do with "stock Android".)