Preferences for accounting software

[Kaarel]

Sorry if it is a bit off topic but we are in the middle of deciding
whether to use GTK for our next product or implement it entirely in HTML.

The product is an accounting software. It should run on multiple
platforms, it should be easy to use SQL server in the local machine and
in the remote server, it should be easy to use the product *securely*
remotely over internet, it should be easy to view and print all sorts of
graphs and reports and so on.

So, can someone give some pros and cons of using a standalone toolkit
like GTK to develop an accounting software instead of using (X)(D)HTML?

Kaarel