"Works the same" in terms of WiFi performance/range? No. Antenna orientation depends on what you want to cover the most. WiFi has a doughnut-shaped radiation so if you place the antennas all up, it's used to better cover horizontally. If you tilt them a bit to the side, the antennas will better cover vertically and still provide good coverage horizontally
if you put them all flat, you'll shoot for covering vertically at a huge expense of horizontally
