ASP+ Was I believe the pre-beta designation of what is now ASP.Net. Main difference is that ASP is interpreted while ASP.Net pages are compiled down to byte code at runtime. This improves performance. From practical point of view, ASP is now deprecated & most new development for MS stack is being done on ASP.Net 2.0... HTH
Yup, i would definitely go with asp.net if you have the chance, but if you are forced to use "classic" asp, it's still a nice scripting language