I use my browser for online shopping. It lets me choose from all shops, so I can choose the price, quality and delivery data and a payment method that I prefer.
Apps usually are bound to one shop. So keep your freedom and don't use an app, that limits you to that shop.
Nowadays there are a lot of mobile applications are available in the play store for online shopping, but which one is the best among them concerned about price, quality, delivery date and payment method.