They are two different species, but they have many similarities.
"Regular" Sailfin Tang is Zebrasoma veliferum - originates in central and south Pacific.
"Red Sea" Sailfin Tang is Zebrasoma desjardini - also originates in central and south Pacific.
Check out Scott Michael's Pocket Guide to Marine Fishes - you can see the distinct differences between the two.
Both very nice fish - both have the potential to get very large - 15.7".
Jenn