Let's say I screenshot with Gyazo. It immediately creates the screenshot online and copies the link to that screenshot to my computer's clipboard. I can literally create an image and share it on here within two seconds.
Yeah Gyazo is great, uploading the part of your screen you want to share just take a sec, it automatically upload the selected screen part and open your browser/new tap with the image link to share! :D
with Alt+Print Screen i have to open paint, place it in paint, cut the right part out, save it, go to a site, select the file... >.>