16:9 is the normal aspect ratio for most of today's devices. Scratch, however, runs in 4:3. Which is totally fine, since nobody's complained. But YouTube works mainly with 16:9, so... I tried to see how high a quality a 16:9 project would be. As in, "how much screen space do I lose?" It's not bad. You lose 88 pixels off the height, which is normally 360 pixels. If we use 272, multiply it by 16 / 9, we get ~482 pixels for our new width. And a format animators can post to YouTube with if they desire. Also, really interesting meta thingy To change the size of sprites between aspect ratios, the size changes to 3 / 4 going into 16:9 (100 > 75), and 4 / 3 going into 4:3 (75 > 100).
