Developing a website for 3 mln. users: SharePoint OR pure ASP.NET?

Question

We need to develop quite a powerful web application for an investment bank. The bank IT would like us to build it on top of the SharePoint platform, but we would prefer to do pure ASP.NET programming.

The web-app should have the following characteristics.

1) It will be a site for bank's clients that will allow them to view their stock portfolios, get miscellaneous reports with graphs and charts, etc.

2) The web-app will also allow clients to send orders to the bank to buy stocks and perform other financial operations.

3) The number of users will be approximately 3 000 000 (total) and 20 000 at any one time.

We have never made any SharePoint programming, but as far as I know, SharePoint is primarily designed to create intranet sites for colleagues to communicate with each other and work more efficiently, to maintain a document library, etc.

However, the bank IT told us that SharePoint has in fact lots of other features that will help us make the project more efficiently - for example, it seems that SharePoint has some built-in scalability and high availability technologies.

I heard saying that SharePoint development is very tedious, that the platform cannot be very easily customized, etc.

The question is: is it better to create our web-app on pure ASP.NET and deal with scalability and other issues ourselves, or base it on SharePoint - taking into account that the web-app we need to create is non-standard and complex?

Thank you, Mikhail.

UPDATE

In the answers, someone suggested using ASP.NET MVC. My another question is: should we use "classic" ASP.NET or ASP.NET MVC for such project (if we leave out the SharePoint option)?

Answer 1

Do you need document management? Do you need version management? Do you need to create "sites"? Do you need audience filtering? Do you need ECM (fancy word for CMS), Do you need collaboration stuff on your site? If your answer is no then SharePoint is not for you.

You said "We have never made any SharePoint programming" and for that reason alone I think you should not use SharePoint. You also say that your app is going to be "non-standard" and complex, another reason not to use SharePoint.

Sounds like you know ASP.NET so I would advice to stick with ASP.NET or ASP.NET MVC.

Hope this helps