If I were contemplating either of these upgrades, I would gravitate towards the engineering approach suggested by Callaway. Afterfall, they designed and engineered their C6. Upgraded the parts prone to failure and considered the entire vehicle in the conversion, not just the supercharger addition.
Ramp Chevrolet on the other hand is strictly adding a part and then dyno tuning the engine's computer for peak HP (and driveability hopefully). However, if your new found 735 HP happens to snap any of your drivetrain components in two some where down the line after several full power runs, guess who's going to have to pony up the money to repair or replace the items?
Just my thoughts. YMMV.