I think they are more or less the same thing but different companies selling/marketing them. WH and Duff's offer 'long travel' and JBG offer 'Super-Flex'. They are meant to do the same thing; flex=travel. JBG offers two different lines of springs...if you are going to buy from JBG, buy the Super-Flex springs (they are a little more $), they are manufactured by Deaver, who makes excellent springs made in the USA--a favorite of off-road racers and rock crawlers alike. BCB also sells Deaver rear leaves, i think they have their coils done custom.... Duffs and WH dont sell Deavers, I dont believe. If I remember right WH sells Nationals (leafs) and I am not sure about their coils. You can do a search on springs and fish through the posts to find who the Manufacturers of their springs are. I hope this helps get you started. Good luck.
John