I reckon it depends on the characters. If its a repaint of the same character, I ignore it. But if its the same mold of different characters, if I like it enough, I'll get it. This is especially true with Sideswipe, Red Alert and Sunstreaker as well as Prowl and Bluestreak... I mean Silverstreak... along with the Seekers.
Really, its a matter of taste I reckon.