Proportions of types of helmets, hmmmmmmm.Partly depends on class of soldier. Older and out of fashion helmets would be worn by poorer footmen. I believe bascinets were right out by 1450. Probably turned into other pieces of armour.
My speculation is-
among Men at Arms/knight:
Sallets 50%
Armets 30%
Grand Bascinet or other heavy styles 10%
misc others 10%
among footmen:
sallets (probably open faced) 40%
kettle hats 20%
other styles 10%
unhelmeted 30%
This is based on extant helmets, pictorial evidence, written accounts (ordinances, etc.), for the latter half of the 1400's.
I don't have an opinion about how reenactors utilize historical helmet styles. Most use helmets that aren't shaped properly and would not qualify as reproductions.
Just my feelings......
------------------
Cheers,
Jeffrey