Do you have a budget in mind?
Acer has some great Windows 8 tablet offerings at around the $500 mark.
And as with all Windows 8 tablets you get a full fledged desktop environment so you can alternatively use it as a laptop replacement, something you just cannot do on Android or IOS tablets. It would be very hard for me to imagine getting anything BUT Windows 8 tabs at this point, unless of course the budget restraints.
At the $200 price point the Nexus 7 wins, at $300...