1 week training regarding App development

Apple, Android, Blackberry apps - I am looking to understand the key differences, pros and cons, costs and timelines, of developing smart phone/tablet apps for Apple, Android and Blackberry, compared to just having a website. Why should I take a web front end to a database and actually create an app in any/all of the formats. What are the things to watch. What commercial models do the different platforms have. I'm looking for a few pages of written explanation of things to note, a comparison table between web only and app development (for each app platform), costs, development issues (typical time, developer resources). My app would be the front end to simple SQL database, which holds people data for an HR system.