Need a little tire help regarding R competition tires.

[67rsconvert]

I am getting ready to order tires for my car and have found some competition rubber for the rears that will fit 19" rims. Width is 265/30. I can buy extreme performance tires(next step down) that are about 1/2" wider tread(best guess) in a 275/30. So am I ahead in traction with R compound or is the loss of width going to negate that?
Tires in question are the Bridgestone Potenza Re-01r and Michelin Pilot sport cup competiton.