Overallly, Drks are generally more beautiful and more powerful than Viper.

Lets see DrK. DrK have slash blust, dragon buster, dragon fury, dragon roar and rush. These skills does pretty high dmg, with sacrifice, dragon blood, beholder's buff, berserks and maple hero which are the signature of drk. I won't say more on pirates as it loses drk completely.

For pirate, I will recommend infighter as it consumes least number of pots with the skill energy sth(sry tat i dunoe tat name) besides cleric if u use it right when 3rd job.

So, Drk are better than Viper