Here is my contribution to this "weight" thread. This simulator calculates climb times for local NorCal climbs as well as famous Euro climbs such as Alp D' Huez. You input, rider weight, equipment and watts. A reasonable but challenging power to use is 200 watts. I would use the default settings for the frontal area and drag but you can play with rolling resistance and drive train efficiency. I have found the simulator to be very accurate especially for the steeper climbs.

I ran a few cases for Alp D Huez, 8.1 miles, 8% grade, 3410 foot climb assuming a base case of a 150 pound rider at 200 watts with all other settings at default values.

150 pound rider = 1:13:17
151 pound rider = 1:13:41
160 pound rider = 1:17:15
150 pound rider @ 210 watts = 1:10:00

1 pound increased the time 24 seconds
10 pounds increased the time 3:58
10 watts more decreased the time 3:17

And of course .1 pounds would save ~ 2.4 seconds. I will take a hill climb win by 2.4 seconds.

I am assuming rider weight and bike weight are the same. In fact, they are probably not the same in actual human performance. The more weight one carries the higher the internal body temperature for a given power. As temperature increases, power production typically is limited or goes down.

I am an incremental improvement guy who likes to ride nice bicycles. I will not say that lighter is always better but from a pure physics standpoint lighter requires less energy to lift up a hill. YMwillnotV.