I've gone over Hasbro's Legend Shockwave before and Takara's Shockwave is a straight repaint with an additional Crashbash repaint included.
While Hasbro's Shockwave is deep purple, Takara's Shockwave is lilac which emulates his G1 colours more. I really like the painted chest frame on him. But besides paint differences it's basically the same figure of the fantastic legends Shockwave.
Cancer which is a Crashbash repaint is included as an accessory. I don't own Crashbash but that is one smug looking face and it's great!
I like both figure so pick which colour you prefer!