Bullet construction changing expansion characteristics is completely unrelated to bullet weight.
You would need to compare identical bullet construction at identical speed of impact to make a meaningful comparison.
For example, Barnes makes their TTSX .308 bullets in 110, 130, 150, 165, 168, 180 and 200gr versions. I'm not positive but I would imagine (it only makes sense) that the part BEHIND the expansion cavity is where the majority of the weight difference resides. Meaning that the difference in weight has little bearing on expanded size.
A reasonable comparison would have to eliminate all variables as much as possible except weight.
Two completely different bullets that ALSO happen to be different weights and expand to different diameters is meaningless.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.