Either a full Windows 8 tablet or an Android but not a Windows RT it is terrible. So much so that Asus, Lenovo, Samsung and Dell, all of who supported RT when it launched have abandoned it now. Currently Microsoft are the only ones supporting it. RT is a tablet built version Windows 8 but it's limited in what it can do and can only run specific programs, which is why the others abandoned it. And with Microsoft being the only ones to support it your options of what you can run on it are also limited.
You would be better off going with either a full Windows 8 tablet or an Android like the Google Nexus 2 for example.