Well yeah, I know the loot is doubled, but I am hoping for something extra for 16 mans. What is to prevent 16 man guilds just breaking up into two groups of 8 mans and getting the same loot with easier mechanics? Besides bragging rights.
I think the chance to get Qyzen's Kephess skin is increased, but I'm not sure.
Mostly it's just bragging rights. Heroic 25 man in WoW has always been the way people keep track of World Firsts. It's pretty much the same for SWTOR,
people will clear 16 man and then start farming 8 man after they've done it once...