Apple iPad is most popular than Microsoft's Surface tablets because of more productivity and repair-ability according to the ifixit.com. Reducing the prices of Surface RT by Microsoft also reflects the less popularity of Surface Tablets.
Microsoft has also said that they are write down the $900 million for not sold Surface tablets by the Sellers. On the other hands, the Apple has already soled 100 million devices of iPad series. This shows and confirm the popularity of iPads against the Surface RT Tablets. Many parents prefer to buy iPad for their kids rather than Surface. The Microsoft Surface, according to ifixit.com also difficult to repair and the iPad is easy to open and repair when you find problems in it technically.
Other than households and personal, the large companies also prefer to purchase iPad against the option of Microsoft Surface rather than the Surface has additional ports, USB Drive and microSD memory card slot in it and also handled with Pen drive provided with Surface Pro versions of Microsoft Tablet models. The consumers want reliable and repairable tablets not more options in it today which Surface did not give them as iPad. As the Google has also Nexus in their store and Samsung has Galaxy Tab but the popularity of iPads is at the same stage at victory stands.