compression or flow?

That's gonna be more a function of the cam and vehicle setup rather than the heads.
True
No street motor lives in those rpm ranges anyway.
Only when racing, this where the OP should decide what he values more driveability, an hp#, track performance etc.. The more things you want your car to do generally the less efficient it becomes at doing any of them.

If 3.55 are a must I'd build for that. (Peak hp around 5200-5600 rpm.)