is it worth swapping 10.7 inch discs for the 11.8 inch?

The brakes aren't the whole story. Just like having a bazillion HP won't do you any good if you can't put it to the ground, having all the braking power in the world doesn't do you any good either if you don't have the traction to take advantage of it.

I wouldn't be at all surprised if it didn't make any difference whatsoever on a set of factory bias ply's. Or even on a set of 205/65/15 BFG T/A's.

But I do know that with the 275/40/17 modern compound radial tires I have on the front of my Challenger, it makes a difference, and a noticeable one at that. And the physics says they're good for about an 8% increase in stopping power. But that's only if your tires and suspension can put it all to the ground.