I can't attest to the cost differential between the two, but the gable roof will be easier to construct, and regarding traditional architecture, it lends itself more to the addition of dormers than the hip roof.

A hip style roof has greater surface area and requires more complex framing with compound miter cuts. Higher costs result from a greater level of skill to build, larger framing lumber, inability to use pre-fabricated trusses, and a generally higher cost for roofing materials (sheeting and roofing) than siding used on a gable end.

Thats the facts on cost, Gable roofs have a simpler construction and appearance, lower cost, and are more prevalent on production housing.

The surface area for a house with a hip or gable roof is exactly the same. I think that labor (and, perhaps, know-how) is the only big cost difference.

goods site for pricing is matplex.com. it compares prices for you

While I realize that cost is a big factor here, also consider how the roof style blends with your overall architecture. You don't want to have a roof that stands out in a negative way. Are you using an architect? If not, perhaps find one who could give your plan a quick review to see which fits better.

What are different solutions for painting a hipped interior ceiling/