I have used iTabs, Android devices and Windows tablets. No worry windows 8.1 is just fine tablet environment! They each have their good and bad points, but these new Nokia Tablets have really upped the Windows tablets in hardware aspect. Surface 2 is allso good but these have better screens (IMHO).
The operation system choise is difficult one. It depends on what you are going to do with your tablet. iPad just works! It is light, it has a good screen, a lot of apps, but it is expensive. Android tablets has more alternatives to chose from, so there is more competition even within. So is has been the economical choise. Windows based tablets have really good pre installed programs. The office pack makes Windows tablets allmost a laptop alternative. The bad thing is that there are not so many aps to chose from. I would really much like to see good music and video editing tools. But otherwise the gap is in practice really small.