So, it's completely dependent on the fight. In a short fight (read, soloing most mobs one at a time), yellow's going to do more DPS because it ramps up faster and is all about instant damage. In a longer fight, red line will absolutely out-DPS yellow in comparable gear by a factor of 150% or more. That said, the fast burn combo I listed will almost nullify this argument in most scenarios, as it turns red line into a burst DPS temporarily.
Edit: I should also qualify that yellow has one huge advantage over red: mobility. If you have to run and/or kite the mob to survive the fight, you can do that in red, but only using yellow line abilities available to all RK's.