Certainteed or GAF Shingles which are Better?

Can't decide on which Roofing Shingles to use. Certainteeed ENERGY STAR rated shingles or GAF Timberline Prestigue 30 year. I can get a $1500.00 Federal Tax rebate with the Certainteed, but are they as good as, better or worse than the Timberline. Roofing contractor is charging the same to install both.