When you order online it is expensive than the market and you cannot inspect the product quality, working, accessories etc before payment.
Shops have cheaper products(but not always) and you can check the product before buying (again not always as many shops wont let you open the box if you have not paid but atleast you can be sure that it is the same product that you are paying for and not a different variant or copy). You have to realize that online stores buy most of the stuff from local market and you can find products cheaper if you know the right shop.
If you go to a shops in places like hafeez center and hall road you can easily get the product replaced if it is defected (in most cases), even if you have bought a used device replacement is easy if you have talked to the shopkeeper beforehand.
Lastly online and normal shops both can do frauds so there is no difference there.