So, here's the thing.
Let's pretend just for a moment that he's just as good either way.
Most attackers aren't. Most attackers are going to need that speed.
You only have so many +20 speed Offense mods. Do you give them to the toons who need speed or to the toon who doesn't care because they're just as good fast or slow?
Of course you give it to the toon that needs speed, since you would ruin that toon to deprive it of speed, but you won't ruin DDK.
Give your low speed Offense mods to DDK. Someday when you've been playing the game for 12 years and have more +25 speed mods than you know what to do with, this will be a legit question for consideration, but for anyone with a limited number of high speed mods, you're always going to have someone who needs the speed more than DDK does.