split and DD simultaneously

6d, S17, DAS
e.g. u may split AA vs 6 and DD, so $100 become $200x2 hands=$400,
can split &DD on KK but not KQ and all pairs as u like.
u may split 77 vs 7 without DD.
what is extra adv ?
my hand cal is about 0.5-0.6%

thks