an answer or so
No VP expert here but there are only certain VP games that offer a positive return and a few others that work out positive when you figure in related comps and cash back. There are VP websites that give you this information. It is based upon the game and it's pay schedule. If you check a typical casino floor you might see the same exact game but if you check the amounts they pay for different hands, you find one machine offers more than the other.
DD is a more favorable game than a shoe if the rules are close to the same. I know of casinos where the 6D game is S17, double any two,DAS, good penetration and late surrender but their DD game is H17 double 10@11 only, no DAS, 55% penetration and no surrender. Here you have about as good a 6D game that can easily be found combined with about the worst DD game.
For counting purposes it is often easier to count the shoe because all cards are up. In a hand held game you need a system to make sure you count all the cards and only count them once.