Twin Turbo 318 or Twin Turbo 225?

Well I originally had a turbo 4bbl draw-through setup on the 225, but I pulled it because it was an original 100k mile motor and it burnt 2 qts. of oil on me in 37 miles, so I decided it was time to rebuild or retire the motor. I've been looking into costs and part availability, and the 318 obviously has more options, especially for ignition. I'm trying to find a mild cam that has center at about 114°. Forged Pistons and Rods are going to cost me approx. the same for 2 less cylinders. I want to make a high horsepower slant six beast. I want to get to the mid 600 horsepower range (if possible)