Are you asking about performance or sound? Cause in the performance department i doubt you'd feel a difference. Soundwise I'm not a fan of the X-pipe tone, Prochamber gets my vote
What kind of mods do you have? 1 3/4 inch primaries and a 3 inch exhaust is really big. You will lose a lot of low end torque(this is assuming you don't have more than usual h/c/i).
Anyway, I would just go for whichever one is cheaper. Both sound good, and both will make around the same amount of power. Preference of exhaust note would be the factor for me.
You may want to get the BBK just to keep it all in the family. Sometimes they seal better when they're the same brand. Otherwise, my vote is for the ProChamber, for both power and sound. I had one for two years, and wish I still did. I'm curious with 5.0GT on this one- WTF do you have under the hood to justify that exhaust? If you don't have at least a heavily built 351 in there it's going to be a complete waste, you'd make more power with a smaller one. Those sizes are optimal for more like a 393 stroker, or 20+psi of boost.