While comparing the sizes of the .jar file of both the libraries, Glide is almost 3.5 times larger than Picasso in size.
both libraries have almost same syntax if you want to simply load the image from the URL and display them into the image view.
One thing in which Glide dominates is, it is designed to work with Activity and Fragment’s life cycle too. You can pass the activity or fragment context with Glide.with() and it will brilliantly integrate with activity lifecycle callbacks such as onPause() or onResume().
Both the library supports caching the image in the disk.
By default, Glide uses RGB_555 configuration while Picasso loads images in ARGB_8888 configuration to load the bitmap into memory.
But while loading the image from the cache, Glide wins the battle. This is because of an advantage of the way Glide was designed. While the Picasso causes some delay on loading since it needs to be resized the image first in real-time before images are set to an ImageView. Even if you use .noFade() to appear it instantly.