Level of expertise. It is something that should be taken into account first. The reason, among all the other points, is the following one. The demand for android mobile app design and development services is high at the moment, so a lot of companies popped up just to provide end-to-end services according to the market demands. Their experience and expertise not always can be rated high. So it is a big question if such a company is capable of providing a reliable Android app. Another thing is the technology list your potential android web-based development services will use. Have a look at the reviews of the customers and the portfolio.