I took em both to the range yesterday. Wasn't even close. The .50 is like a nuclear bomb. Very uncomfortable to shoot. The .500 is smooth like butter and manageable. For WOW factor, it's the .50 all the way
I think the difference is mostly dependant on the choice of ammunition. There is such a wide variance of energy and recoil impulse that depends on bullet weight, powder charge, and propellant burn rate that it would be very hard to compare two guns that use completely different cartridges like the ones I pretended to review here. Also, most of the off-the-shelf factory ammo in .500 S&W is pretty anemic. Glad you enjoyed shooting these big guns. The WOW-factor is definitely what it's all about!