Easy solution. If you prefer the bigger ipad, stick with it. If you like a smaller one, hope they produce one and buy that. Done. Personally, I hope they make a bigger iphone so I don't have to carry 2 devices around.
With the mac pro, it pretty much is about OSX, well that and powerful reliability, but yes the hardware could be duplicated in a PC, but the Hackintosh solution isn't going to work for most people. Too risky.