Host and manage a Web API

You are working for a large company that has a lot of maintenance engineers on the road. You are going to develop an app to support their work remotely with publicly available data. You are looking at your deployment options. You know the app will be used during office times. Throughout the day, you will have five thousand users of your service. What deployment option do you choose?

You use Azure Cloud Services to host your Web API as a Web Role.
You use Azure websites.
You deploy Azure Virtual Machines to host your Web API.
You buy extra servers for your on-premise data center.