Dragon scimitar is the same speed as whip and scimitar. It all depends on experience rates, not personal choice simply enough. I think it has been stated many times that Dragon Scimitar has a higher rate of experience gaining than the Dragon Longsword, that is basically the end of the thread. I quite like the Dragon Scimitar's special attack, I think it looks cool and it earned me a glory amulet in an iron war once. Some level 126 was protecting from melee while getting piled and I Severed her and she got decimated in the 5 second period.