Is there any mapping document provioded by Aspose where one can map the ppt classes and methods to corresponding pptx classes and methods.
I have observed the requirement shared by you and like to share that PPT and PPTX are internally two different formats. So, there is no mapping available that if some thing is done in some way then how it can be achieved in case of PPTX. Although, online sample provides some sort of indirect mapping in a way that they are shared for both PPT and PPTX and you can observe from there that how two things are managed in PPT and PPTX.
Secondly, we are at present working over unified Aspose.Slides Api whre we will have single API for PPT and PPTX. The said API will be rolled out by Q4 of 2013 and we will share the good news with you when it will be available. It will make things simpler for you then.