I would say the Grant Last. While the Barrie may be a bit more generous in terms of volume, I have found the Grant to have a similiar fullness to the Barrie and narrower in the heel. I have a pair of the Cigar Shell captoe boots, and have found this combination to make for a very comfortable boot.
Are you same size in Barrie and Grant? Or are you 1/2 larger in Grant i.e. more TTS?