It looks like the new X is more intense, either for big people, a few parts of the upper thight, people using it more for joint compression for an injury, etc. The regular will probably be your bread and butter band, though. Jumping straight to the X would be tough imo, the regular is already torturous. 

I have both. There is actually very little difference between the two. If you don’t have either get the Voodoo X. If you already have the original Voodoo band there isn’t much reason to justify buying the Voodoo X. The bands are as torturous as you make them. Don’t wrap it as tight if you think the Voodoo X might be too much. The Voodoo X band doesn’t narrow as much for the same amount of tension as the original Voodoo band. This makes it less likely to cut into your skin and get uncomfortable. The Voodoo X is less likely to roll up on you when doing the upper thigh, but it’ll still roll up.