There are a lot, in theory and practical both :). Let me list out quickly that comes on top of my head right now ....
1. ASP uses vb as server language <-> ASP.NET can use C#, VB.NET and other .net supported languages
2. ASP doesn't have its own control, it uses html elements <-> ASP.NET has its own control to increase developers productivity and ease the development.
3. ASP doesn't have ability to define master page/template to simplify the design and maintain uniformity <-> ASP.NET has master page concept, themes to simplify the design and maintain the uniformity across the application/website
4. ASP is not purely object oriented (someone can argue) <-> ASP.NET is based on object oriented architecture, everything is an object here
5. ASP has only one way of designing the application <-> In ASP. NET we can use ASP.NET Web Forms, ASP.NET MVC, ASP.NET Web Pages patterns or architecture to develop applications
6. ASP doesn't have its own authentication mechanism <-> ASP.NET has many built in feature, one of them is Forms Authentication through which you can implement authentication and authorization.
7. ASP code is not complied when it runs on the server <-> ASP.NET code is compiled when it runs on the server.
8. Building a custom control in ASP is not possible for a specific feature <-> In ASP.NET you can build your won custom control and share across the application or another application.
There are tons of other benefits, if you have to make a decision to use ASP or ASP.NET, use ASP.NET for sure.
Hope it helps.Maheshvishnu, if this helps please login to Mark As Answer. | Alert Moderator