I've been a fan of the Advance Wars series since the first iteration. This game is the first of the series on DS, and honestly, does not utilize the dual screen capabilities very well. This game is inferior in almost every way from its predecessor, but is still pretty good in its own right.
Dual Strike has two major changes, Dual screen maps and Tag Team COs. Dual screen maps were just tedious, as basically they force you to fight two separate, practically unconnected battles at the same time. Also, many times you cannot fully control the AI CO fighting for you on the other map. Tag Team CO powers was an interesting idea, but the execution is horribly flawed. A single usage of the CO power can drastically change the tide of battle. You can be on the verge of victory, then the computer uses the Tag CO Power and decimates your attack force. Also, by using Eagle and Sami to tag, you can move an infantry that is 21 spaces away from the enemy HQ and capture it in that same turn.