You can shoot a laser in the air and keep moving in the air. Which means, you never have to commit yourself to a specific area on the ground. You can shoot in the air and quickly move to a better positioning, making you harder to punish. Ground lasers limit your movement, while ariel lasers keep you free and unpunishable. This is key in a game where control over the field means everything.
Plus, SH'd lasers can change in height and they're harder to predict. SH'd lasers can also stop opponents from jumping. Basically, SH'd lasers have less lag, give you more options and let you keep your momentum. They can also be buffered at the end of a jump or a move, to really throw your opponent off guard.