A world of difference!
1 advantage would be run time speed.
1 disadvantage would be the learning curve.

>Out of curiosity (and interest too) Is there a lot of difference between ASP and ASP.Net. Advantages, disadvantages? Is it better to do stuff in ASP.NET? I did a bit of ASP in the past and we received DVDs from MS with trial version of .NET and we wonder if it is really useful to make the switch or stick to VS6 for now.