That's an EXTREMELY open-ended question. Basically it comes down what do you plan on doing with it? If you just want it to surf the web and watch videos and such, then it pretty much comes down to which companies interface you like.
If you want straight up Android with faster updates, Nexus 10. If you want bells and whistles, Samsung Galaxy 10 or Galaxy Note 10.1. Kindle Fire HDX is only 8.9" but it's a really solid tablet if you want it for multimedia/reading stuff. If you want to be able to use a stylus to do things like sketch and take notes then Samsung Galaxy Note 10.1 or, if you REALLY want a powerful stylus and want to do heavy duty illustration and photo work Wacom's Cintiq Companion Hybrid 13.3" tablet. It all comes down to your needs.
If you just want a good solid tablet with solid specs and no stylus, probably the best Android one out there is the Nexus 10 though.