Energy efficiency

Last year we purchased a midcentury modern home, age 50-60 yrs. The majority of the home has tongue and groove cathedral ceiling. Because of some leaking skylights we decided to "bite the bullet" and replace the leaking windows and aging asphalt shingle roof. Since that time we have learned many things about roofing. In an effort to be more energy efficient, we considered several different concepts. Our problem is that we want to get the best solution but don't know how to get there other than speaking with several roofing contractors in our area. They are among the best in our market but don't seem to have the expertise to discuss our dilemma. Our roof is 2-12. It has no venting. We believe there is one inch iso on the roof now. We have been advised to install a crossvent rb venting system and additional iso and 30 yr asphalt shingles by one contractor and a metal roof with: 4. Install high temperature ice and water shield to the existing wood deck. 5. Fabricate and install 1-1/2” standing seam metal roof system with all associated perimeter and penetration flashing using 24 gauge galvanized steel pre-painted with a Kynar 500 finish. Panels shall be continuous in length. All seams shall be double locked. (Color choice to be selected by homeowner.). If we install the metal roof, we understand the benefits of how the painted finish will help with cooling costs. We are not sure of the energy benefits in the winter. We have been told the metal roof is so efficient that additional thickness of iso board 4x8x3 would only give us an R16. The benefit does not seem to justify the cost. We have also been told the metal roof is so efficient that a crossvent system would not justify the added cost. Please give us your input. Thank you