It's still is going to come down to velocity , port volume and runner length. a head that is too big is going to have a lack of low end-mid range torque, I just don't see any other way around it and really show up on the track. a head that flows a certian cfm could have a different port volume from a head that flows the same cfm but they both make different power. higher port velocity + higher air speeds fills the cylinders faster, so even though a given head flows X cfms it's port may be larger than other head flowing the same cfm's and thus producing slightly less hp due the drop in velocity. OK next.
I agree, some cylinder heads are just flat out better at flowing air than others, regardless of runner volume, or more importantly, cross sectional area. Any head that flows the same or better than an equivalent head with more cross sectional area is obviously a superior design.
I don't necessarily jive with the notion that big heads kill low end torque. That's kind of a generic slippery slope statement. Like anything, it's all about the combo. If cam and intake are selected properly, "big" heads can achieve respectable torque numbers at "low" engine speed. To what extent and how far that can go, well, I intend to find out. Once I get this together and running, I fully intend to take it to a dyno and see what happens.