In a theoretical world Stinky is correct in his statement that penetration will be equal.
Penetration is reliant on two factors. Sectional density and velocity.
So if velocity is equal and SD are equal the 200gr .30 caliber bullet and the 6.5mm 147gr bullet will both penetrate the same amount. Let's call it 30 inches for now. This is also assuming neither bullet deforms and the SD remains identical in both cases.
We all know the energy of the .30 cal bullet is higher and it uses this energy to create a larger wound channel but penetration is still equal. Energy equals work, or damage in this case.
But we don't live in a theoretical world where bullets don't deform, in fact we want them to deform.
SD is still important for terminal ballistics but it changes as soon as the bullet deforms and sheds weight.
Let's assume 80% weight retention and double diameter expansion.
147gr 6.5mm (0.2644 diameter)
147/(7000*0.2644^2)=0.300 original SD
117.6/(7000*0.529^2)=0.060 terminal SD
200gr 0.30 cal (0.308 diameter)
200/(7000*0.308^2)=0.301 original SD
160/(7000*0.616^2)=0.060 terminal SD
Well I must admit I wasn't expecting the same terminal SD
So penetration will still be equal if both bullets deform and shed the same proportion of weight. So penetration is really dependent on bullet construction! Which we all knew already, right?
So yes, Stinky is right, penetration will be the same but the larger bullet will impact with more energy creating a larger wound channel.
Now whether a 0.529 inch hole through both lungs is significantly different than a 0.616 inch hole.....I don't know that equation, sorry.
Shot placement is always key. So if you can shoot your 6.5 whatever more accurately than your 0.30 whatever then the 6.5 will perform better. If you can shoot whatever your using accurately you are good to go.
Now where was that recoil thread?
