Content blocks in the Drag and Drop Editor that contain images have three different buttons that show up when you hover over the image: an orange link, a blue camera, and a gray trashcan. The trashcan will remove the image, the camera opens your computers saved documents, and the link button allows for access to the image properties pop-up and the media gallery.
Both the blue camera and the orange link button allow you to add an image to the block. When uploading an image using the blue button, the editor lets you zoom in/out and move the image around (after zooming in). When you click ok, it saves the manipulated image at the size it was cropped at and sized in the editor. When uploading an image via the media section, it uploads the entire image at it's original file size and dimensions. When you choose this image from the gallery in the orange link button, it scales it to match the current dimensions of the previous image in the editor without actually modifying the image file size or original dimensions.
Using the blue button is similar to opening the image in Photoshop, shrinking it down to specific dimensions and cropping out what you don't want in the image and saving it. The media uploader just uploads the original image without changing anything about it. This typically produces a higher quality image because there is no zooming in/out before saving.