Better roof longevity: composition or concrete?

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Q: My husband and I are having a new home built in the California foothills. I resisted suggestions to go with vinyl windows to save on cost. The latest struggle is the roof. The architect designed the house with a concrete tile roof to go with the English Tudor style. My husband and the general contractor have been encouraging me to consider a composition roof to save money, and I suspect, make the process easier for the contractor. The only concern I have is that the roofing companies and the general contractor advise that concrete tile roofs do not repel water the same as a composition roof; they claim that the underlayment is the only thing that keeps moisture and snow effects from infiltrating the structure below. Is this true? This will be our retirement home that we plan to live in for the next 35-plus years, and we don't want to be worrying about a roof replacement while in our 80s or 90s. Anything you can provide to reassure me that holding fast to the decision to...