2D vs 3D mesh deformation.

So I am creating a primarily 2d game with a few small 3d Aspects. Right now I am trying to figure out which would be easier to use for mesh deformation / destruction. You can see a screenshot of my games pre alpha state right here as you can see the ship shoots bullets and those bullets hit planets and are destroyed.

Currently the planets are 3D but not for any real reason (they can be changed to 2d easily) So what I am trying to do is have these bullets basically "delete" or "remove" chunks of this planet as it hits them. Think Worms Armageddon Where bigger guns do more structural damage but the overal structure is still intact. Does anyone have any ideas for this? The reason I bring up 2d and 3d is I do not care which one I use and I figure one of the 2 engines is probably better at this sort of thing.

Any info would be great, this will not only be visual but it has to actually change it bounding box, for example a player needs to be able to shoot a planet in half and fly through it (not the primary goal but you can if you want)