I need to create a GIS web application for my startup business, and sell access to it on a SaaS model. Our app will plot and analyse a range of different geospatial data sources related to land use. Importantly, we want to compare attributes for similar polygons (in our main case the polygon would represent a property). User experience is very important as users will be non-GIS people. Ultimately we want to be able to expose our database to an analytics engine. What platform should we use to build our app? Should we look further than ArcGIS? What are the factors we should consider when assessing open source components? Is there a platform out there that we can just walk up to, load our data and start selling subscriptions to? Or is there a reasonably complete framework we can use to speed up our development time?