ASP .Net allows -- but doesn't require -- MVC design. A design pattern like MVC is easy to slip away from.
First, MVC requires a proper object-oriented Model. Something that VB isn't very good at. Often, the first short-cut is to use a relational model and SQL queries and leave it at that. In an OO world, class methods that are part of the model are sometimes put into stored procedures in the database, other times their part of ASP pages, and some model-level features wind up in separate VB modules.
Python is OO. Django separates the model completely as stand-alone Python modules. You can easily be absolutely sure you have all the right method functions in your model. You never need to resort to stored procedures.
Second, MVC requires a clear distinction between View (as in HTML) and Control (as in the the application processing and navigation.) Sadly, ASP allows you to put anything in an ASP page; too many people start to put everything into their ASP code. Eventually, there's no real distinction between View and Control.
Django separates View and Control. The web site's view (or presentation) is via templates. The rest of the control is "view functions".
The worst case scenario is an ASP site where the essential processing is scattered randomly through ASP pages, VB modules, stored procedures.
The fundamental Django model is URL maps to a view function. The view function returns a template with some values to be displayed in the template. Two very simple things that lead to very clean separation between model, view and control.
Some people complain that Python's template language is "brain dead". Partly this is just their frustration at the absolute separation between presentation via templates and processing in view functions. You are absolutely forbidden from doing anything that even smells like processing in a template -- just present the data in HTML.
Good design work can be done in ASP -- you just have to impose the discipline on your own. I find it easier to do good MVC-oriented design in Django because the framework encourages and supports it.