There is one major factor that everyone seems to be missing here...
In the original video the guy throws the dynamite from the waters end (the rock wall?), no longer than 50 yards from where the explosion occurs. On the show that tries to prove it wrong, but there is nothing behind the explosion to send the water rushing backwards back forward (looked liked it was a river or something). It seems to me that would have alot to do with the wave?
I think the original was for real, especially due to the difference in locations and conditions.
Another thing the mythbusters missed is that the lake has changing depths. the power in the lake just kept goin over the differences in depth and ran out of power. The lake in the video has got to have a more stable bottom.