Best overall review of the 11 inch I have seen so far, from someone who has previously been a 12.9 user. He gives his thoughts on the 11 vs the 12.9 around the 8:30 mark.
Spoiler: He likes both and wants one of each. 12.9 excels for desktop use and 11 excels for moving around/portability and more casual use. Same conclusion as most here have stated.
As Dnichter suggested in his post above, this isn't to say that the 12.9 wouldn't work as a good portable or more casual device, nor that the 11 inch can't be used mainly as a work desktop device, but they seem to be aimed at two different use cases.
In the absence of a strong feeling as to which one prefers (and the inability or unwillingness to spend money on both
🙂 ), it seems to me that the above could serve as a good guideline and a decision could reasonably be made looking at which use case is the primary one.
Just more food for thought for those still on the fence.