Fords 6.2 mod motor is 430 at 4500rpm. I wouldn't call that lower rpm then pushrods. That's a typical rpm range for torque across the platforms(typically 4000-4800). I also do not agree with four valve making more power. Again, it all comes down to valve events, shape and design of runners, combustion chambers, valve sizes, etc. example, the new L86 makes 460 trq at 4100rpm. Its just a combo of valve events (VVT) and DI.
Having built, tuned, dyno'ed and raced a few GM LS platforms as well as building a buddies Ford 4 valve, I will stick with the pushrods for reliability, simplicity, fuel efficiency and power