Small cross sectional area is supposed to be better as xdclevo's said but there are limitations. It'll give better power/torque down low basically upto 5500rpm or so. Beyond that I found a larger cross sectional area will make more power and better torque up higher. For example I'll use CHI's hp flow figures. The 185cc head flows 590hp (1.9) and the 218cc head flows 680hp (2.1).
The basic jist of it is 351's supposedly like about 1.9 and strokers (378 and up) like 2.1.
I've got a set of 218cc 2.1 cross sectioned CHI 3V's on a 351 too
My signature tells the story. I'll update that sig with some faster times. Yes, I am that confident
I am one who tends to run against the grain and get results instead of following others and running all the same parts as other people. Being a sheep ain't my thing.
My personal opinion is 1.9 cross section is great provided you don't want to rev past 6500rpm max. Most decent cams like to go 7000+ with a good flowing head. Thats where the bigger cross sectional area comes in. More rpm and more flow = more power/torque.