Both have their fair share of advantages and disadvantages
Chances of theft: Parking Permit Stickers
are less likely to get lost or stolen because they stick to the outside or inside of the vehicle’s windshield, bumper, or mirror.
Easy to Install: Parking Permit Hang tags
have a special cutout that easily fits over any rear-view mirror of the vehicle, whereas parking stickers take a little more time and effort in installation.
Hang tags are more likely to block driver’s view than sticker permits. Stickers even come with a clear background for more light to pass through them.
Hang tags are easily transferred from one vehicle to another and can be removed for added privacy and security. Stickers, unless they are the cling type, cannot be removed.
Good quality stickers are durable, tear-proof. Hang tags made of thick plastic won't warp, fade, or crack.
Ease of Verification:
While some parking staff members may find it easiest to visually verify a sticker on the vehicle, others may find it easier to glance at the rearview mirror as each vehicle enters the lot.