Honestly, it's impossible to really say and after the well publicized benefits to running economy of road racing product, the fact that there isn't the same for track product backs that narrative up.
Your one key difference (and I hate to say this but this is really the only difference) is the amount and type of cushioning between the spikes. The Dragonfly has more, the Matumbo less. Because of that the Draggonfly is slightly heavier (despite the improvement in foam managing to keep this weight increase to a minimum) but at the same time protects your muscles more from the impacts of running on a firm surface - the performance benefit to that which is still difficult to quantify.
On the flip side the Matumbo because it has less cushioning and firmer cushioning does a slightly better job of maximizing your force to the track surface. Slightly less energy is "cushioned" because there is well, less cushion between your foot and the ground.
So what's better? The pro's and con's definitely offset each other - especially in a racing situation. The Matumbo is lighter and firmer - both benefits vs the DF, the DF has more protection in the way of cushioning that reduces muscular fatigue which is especially helpful the longer you run. I'm kind of surprised we don't see (or hear of) pro's - with unlimited free access to product, training in the Dragonfly but racing in the Matumbo/Victory - that would seem to be the most performance beneficial scenario.
If you can have just one pair though? Dragonfly. Because the benefit of cushioning that cumulates over the course of a season training/racing etc far exceeds the benefits you would see comparing both over a single race situation. Also without a doubt the Dragonfly just feels better - doubtful anyone notices the 25g weight difference between the two but you sure as heck will notice the reduced impact that can help with smoothing out your footstrikes/gait etc.