Depends on what you fly. Some ships just have smashable canopies.
Remember, if you run out of air, your ship EXPLODES.
They all do. Some are more prone to popping than others, that's for sure.
Surface area of the canopy obviously, and position are the big factors.
Ships with a big fat canopy protruding out the front (asp for example) - these babies are bullet catchers. Extremely prone to pop.
Ships that simply have their canopy right at the front, especially ones you may like to face-tank in / have a flight profile that lends towards jousting (clipper for example) - also quite prone to pop.
Ships that have a canopy positioned dead-centre of rotation - even if the surface area is small - are prone to pop. Enemies may appear to be targeting your canopy directly, where in fact they're just throwing stuff directly into the middle of the target, and that happens to be where your canopy is. Can't think of an example ship top of my head, but there definitely are some of these (vulture?)
On the flipside - canopies that have a small profile & are set-in to the bodywork, but not either right at the front or dead centre (python for example) - these tend to be the least problematic.