Well, Rockchip and AllWinner are getting better with 2x speed of Apple and Samsung. Nobody heard of them two years ago, but now their latest processor are made with 28nm technology with the latest ARM platform, such as A7. You can get the latest quad-core 9.7" tablet powered by AllWinner A31s for a little over $200, only 1/3 to 1/2 of the Apple iPad 4 price. Check this out:
I've used one HTC tablet which uses rock chip processors. I would the perfromance is terrible and decided I will never buy a product other than apple or google. But I believe Mediatek will defintely have a much better product.