Here's a couple of links that show a large number of headers and their characteristics:

http://honda-tech.com/zerothread?id=700477
http://www.honda-tech.com/zerothread?id=699674&page=1

unfortunately, all the actual dyno plots in the second link appear to be down. if you're interested in seeing them, email James at Titan and see if he can get them back up.

from my experience, it seems as though headers that possess a 4-2-1 design with stepped primaries (i.e., the diameter of the piping increases as you go from the flange to the collector) and a single wall collector have the smoothest overall power curve and they allow for a lower VTEC crossover in a basic i/h/e set-ups.

once you start throwing in cams, IMs, TBs, etc., things change though.