heeeee...
What about the weight vs lift relationship? Higher weight requires more lift
Now slightly deeper...
What is, in the given case, the difference between the lighter and the heavier craft? Yes dude, weight.
To maintain a given airspeed (IAS), you will therefore need more lift for the heavier craft (climbing, level, descending).
More lift? Yes, increase your AOA. And produce more drag. Result is a lower ROC during the ascent, lower airspeed (or MN or FC) in the cruise, and a higher ROD pointing the nose to the Planet.
(much brain storming in this heat
)