Like you said, it's just for looks. That's the only upside. The downsides include:
1) You have to replace the uppers AND the lowers if you go extended, which costs more money, and the uppers are a pain in the ass to swap.
2) You change your wheelbase slightly, putting even more of the weight of the car in front of the drive axle.
3) You risk needing to buy an extended length driveshaft.