Good question, I've asked the same thing.

Is a large screen better than a qwerty for typing?
-No, but it's close enough with Swype and SwiftKey.

Is a large screen better for gaming than a smaller one with qwerty?
-Not really. Maybe in some instances, but qwerty tactile is awesome.

Is a large screen better "in general" than a smaller one with qwerty?
-Yes, slightly.

Now what about a large screen with a PEN ?
-Yes, it's even better, no doubt.

What if the keyboard is modular, can be swapped out for an extended battery or gamepad with joysticks?
-Hmmm, good question. I think the flexibility of the modular design claims the win, especially since the large "phablet" cant have a portable joysticks/gamepad.


What if there's a game controller (eg Datel TurboFire2) which can dock the "phablet" in, what would be better that, or modular?
--Impossible question. One would be better video and sketching wise, the other better portability wise and gaming. But both solutions very competent in all situations. Even I can't decide.