Hand stretched canvases are the best option because this reduces the possibility of over-stretching. Machines may over stretch the image, causing rips or breaks in the ink of the image. Hand stretched canvases also allow for humans to align the image in a more visually appealing way, being sure not to cut off any parts of the main image which a machine would not be able to detect.
On the back of the canvas, good gallery wraps are stapled cleanly and securely.
Good gallery wraps have clean folds on the edges. You can see the nice folds on the corners that show they are hand stretched, but no extra pieces of canvas are sticking out or causing extra lumps under the image.
Solid Wood Stretcher Bars:
Good quality wraps should have a good foundations. Solid wood stretcher bars provide a good base for stretching and keep the canvas from bowing or bending over time.