It's probably a bit different on a harder target like a helmet, but I know for a fact that both will penetrate about 22-23 inches of ballistics gel.

The Desert Eagle is a silly little thing, one of those "we did it because we can" type deals. The .50 cartridge was developed for the Browning machine gun... not a pistol. A lot of that cartridge's potential is wasted in the DE pistol.

.50 BMG fired out of a rifle or machine gun moves at about 3,000 ft/s. Out of a DE it moves at about 450. And that's low even for a pistol, because the projectile is fucking huge. Our Nagant revolver has a velocity of about 800 ft/s.

Penetration is mostly about velocity. Even though the .50 fires a huge projectile, it only puts it on par with that dinky russian revolver in penetration because it has just over half the velocity.

If you want real penetration on a pistol, you reach for a 357 Magnum revolver. It'll out peform the DE by a mile.