For street and track use you can't go wrong with Stoptech or AP. Both companies are widely used in race series, AP moreso than Stoptech, so you know they are quality and can withstand abuse. What it comes down to is which one you like better in terms of looks and which one has better pad selection and which one is easier to rebuild in terms of parts availability.

 

If you're going just for street use. watch the brakes marketplace for 03/04 mt6 owners selling their oem brembo calipers. Get a set of new rotors and s/s braided brakelines from any reputable manufacturer. Then you have to stress on what kind of brake compound you want to use. IMO, Porterfield is the best. Check out Gruppe-S, I think they have them. Depending on what you're intentions..like having some trackdays or HPDE's here and there. I'd go with the R4...but for street and auto-x, go with the R4S.

You'll save a whole lot of money this way. Only if you plan on doing some serious roadracing or tracking, say like the redline time attack events, where you're at a more competative level. Then I think that's when you should re-evaluate your braking needs. IMO, the factory brembo brakes are more than sufficient to handle FI and the mommentum of the G35. Tire and brake compound choices are what makes the biggest difference for what you already have.

 

+1 for racing brake,got a buddy who has them on his z and loves them.i just ordered my front and rear set from them today and cant wait to get them.