I'm going to presume that the Hyundai is one of their smaller models. If so, smaller cars are more likely to be seriously damaged in an accident and more likely to be totalled, which doesn't bode well for the insurance company or it's policyholders. The Silverado diesel, like most pickup diesels, is a car thieves wet dream. Hopefully Chevy had the foresight to include the VATS anti-theft system on these models, which will keep away the more casual car thief. From that perspective, Ford Super Duty pickups are a trip back to the Seventie's, with just the steering column lock keeping thieves at bay. A talented 12 year old could steal one of those, and it would be in a shipping crate bound to Mexico in about 24 hours.

Anyway, If you can't get a better break on the policy cost, I would take a long hard look at the economics of swapping out the Hyundai for a medium-sized American sedan like an Taurus or Impala. Poorer fuel economy, but probably the easiest class of automobiles to insure.