I prefer the linear ones because more focus can be put into story and gameplay instead of filling the "sandbox" with sidequests and collectibles.
I say open world. With games like Second Son, exploring the world was beautiful, seeing new stuff, you can go to the main story anytime, and such. Open World games are nice, with different events happening anytime and look at Skyrim, Dying Light, they have more content then any liner game with no limits and most of all day/night cycles are great for these types of game.
Can not handle the confines of a linear game no matter how good the story, if i want an amazing story experience i'll read a book or watch a movie.