The raptor talon is going to be stronger overall. I have both of these balls. For a THS, my Raptor is basically unusable. The roll is just too heavy and too strong.
The covert has a similar motion, but much more tamed down. I put a weaker pin in my covert and out of box I found it got down lane quite a bit. I eventually scuffed the surface to about 2000 so it was more for what I was looking for, but this ball is very versatile and I love it.
Unless you are very speed dominate or you have a low rev rate, I would recommend the Covert over the Raptor. Raptor in my opinion is very heavy oil /long pattern dependent. And because it is Asym, it is not as versatile for scaling down hook potential.
Hope this helps.