Dez you're dead right about the difference in portability - while the 12" is not much bigger (longer) and not much heavier than the 10" in truth those differences seem to multiply instead of adding to each other, making the 12" much more of a task to move around manually.
I was very happy with my 10"
and had no plans to upgrade to the 12" at all. It was simply a case of an offer that I literally couldn't refuse came along, and without that I would probably still have had the 10" today otherwise.