which should i use.. i like iron dragon tasks but so far duradel hasn't given them to me.. although like 1k aberrant spectres :x

If you think you could handle the constant high lvl monster assignments then go for Duradel, although you could stay with Chaeldar with mid-high lvl monster tasks and get your combat up a bit more so you could handle the harder tasks from Duradel a little easier. Also seeing as Chaeldar gives slightly easier tasks than Duradel you might find at your lvl you would get faster slayer xp, although I'm not 100% certain on this.

I would stick with Duradel because he gives the highest level tasks, and in the greatest numbers. :

I always found duradel best for melee, chaelder best for ranging.