I must give Samsung credit for at least one thing; they will build anything. Their efforts are an outstanding source of industry research. You can learn quite a bit about what a particular market responds to by looking at the adoption of Samsung products. They make phones and tablets in increments of every inch, and tenth of an inch. That's certainly how it seems sometimes. The point being, if we want to know how different sizes effect sales, we have only to look at Samsung's portfolio.
When Apple first introduced the iPad at 10", we all thought that it was successful, in part, because Apple had figured out the perfect size for this type of device. After almost four years of observing the market, I have come to the conclusion that we were wrong on that point. The success of the iPad mini proves beyond a shadow of a doubt that a diminutive iPad is still just as much an iPad as its bigger brother. The iPad's early rivals tried to match the form-factor, but were unsuccessful in the marketplace. Samsung tried a different strategy. They went for a 7" tablet, largely because it was cheaper. The tablet's failure seemed to confirm the theory that the iPad's size was just right.
Motorola later came out with the Xoom. It went head to head with the iPad in price and dimensions. It became the most high-profile failure of its time. HP was the last company to mount a major campaign against the iPad by trying to match price and size. TouchPad, we hardly knew you. Since then, we have been fed a steady diet of 7", Android tablets. Samsung keeps their 10" lines alive, I think, mostly out of pride. I have yet to see a single report suggesting that they are selling in significant numbers.
Here's the catch: 7" tablets are not selling all that well either. No single line of tablets comes close to matching iPad sales at any size or price. The 7" category is full of $100 - $200 tablets that seem to do well enough in Asian markets where money is a chief concern, and intellectual property is not. Even so, none of the players who are in it for the money seem to be doing very well at all. Apple, on the other hand, seems to be able to sell out of iPads at any size and price they offer them. This tells me that people are not interested in 7" or 10" tablets. They are interested in iPads.
This will be very bad news for Samsung. They have just announced plans for tablets in yet another size. Responding to iPad Pro rumors, Samsung will soon be offering 12" tablets. The rumored price of these new tablets is said to reach upwards of $1,000. Personally, I dong think Samsung is that suicidal. Probably not too long after, I expect Apple to introduce a large-form tablet. I further expect it to sell stupidly well, and not just to me. It is not the size that matters, and in Apple's case, it is not even the price. It is the fact that it is an iPad that happens to meet the requirements of the customer. Big ones, little ones, and all sizes in between: all will sell equally well just as long as they are iPads.
This also tells me that, on the Android side of things, the only thing that maters is the price. The size is just a factor of the price. If bigger tablets were cheaper, android users would buy bigger tablets.