It's kind of like...OK, just saw your edit and the video. Yeah, at 100 yards, the .308 did more damage to the jello, unsurprising, since at 100 yards it has a lot more energy.
I bet the .338 RUM would do even more damage.
The point I am trying to make is that you don't really NEED that extra energy. The damage from the 6.5 in that video was still substantial, with excellent penetration, and would be fatal to any game animal with a hit to the vitals.
You have to go 20 miles to the lumber yard to get a dozen 8' 2x4s. Outside you have two trucks; a 1/2 ton with an 8' bed and 3/4 ton with an 8' bed. Both run great, have 4 wheel drive and full gas tank. Which one do you take?!?!
It probably doesn't matter... right?
WRONG!!! You absolutely have to take the 3/4 ton because it is engineered for more weight! And since you're not going more than 400 miles, no good reason at all to use the slightly more efficient 1/2 ton.