Any question answered...

Do Ultegra 6700 brake callipers / leavers have the same cable pull ratio as DA 7900?

ie if you had Ultegra 6700 levers would the DA 7900's be the ideal match?

Also is it just a weight difference between the DA and the Ultegra callipers?

Cheers.

Ooh ooh it's the question I always answer. ;)

Yes, 6700 and 7900 will match up correctly. The difference is pretty much just weight as far as I know, and even then it's only about 20g / 6% difference for the pair. D-A might be a bit stiffer maybe?