Agreed. This is really just one of those things where you have to try it for yourself to get a good sense of whether it works for you.
Also, if you’re constantly holding the 12.9, it’s going to feel like a beast. If you’ve got it propped up on something or in a case with a stand of some sort (like the MK), then the weight and size is a non-issue. In fact, in that case the size is actually glorious.