People with the larger one will always defend it...
For me, the size is an issue, it just doesn't feel right in my hand and its too heavy to be comfortable. The so called advantages it brings like side by side, notes, or arty things are workflows i just wouldn't ever ever use.. 9.7 just works better for me and with the better camera and new features, the 12.9 has more memory and a very very margin performance gain, but other than that the 9.7 is a better device..
I wonder if that's anything similar to how people with a 9.7" iPad/7.9" iPad/Surface Pro 4/any other device, will "defend" it. Maybe it's something to do with everyone having a personal preference, I'd call it sharing an opinion and an experience as opposed to defending it. The funny thing is, what suits me won't suit everyone else on the planet. Probably why there are thousands of different devices out there, giving people the opportunity to find a suitable device.
Indeed your guilty of that which you deride at the start of your post. By proclaiming the 9.7" to be the better device. A statement which is blatantly untrue. It's the device which suits you best, but having used the 12.9" Pro, I wouldn't own the 9.7" if you offered me it at a tenth of it's price. The screen is just too small to be useful to me.
My iPads (and I've had them all, bar the new 9.7" Pro) have always been consumption devices. I've found the small screens and cramped keyboards too limiting to be anything other than that. Since upgrading, I've never been so productive on an iPad, I get a not insignificant amount of work done on mine now, that's made it even better value for money than they've ever been.
The "so called advantages" as you mockingly seem to state them are things I never used on my Air 2. But since switching to the 12.9", they are all, amongst others, things I now use daily. As for it being too heavy, I've got severe nerve damage, something I have to take so many pills to try and keep under control every day that they could, literally, kill several horses. Yet I manage to hold it, so I'm always surprised when able bodied people complain about the weight.
Actually, that medication is why I'm waffling on just now