No, I have never looked at trichome densities and couldn't anyway since one needs a microscope to see them, see link below.
Here is a link Iknow you'll find interesting.
http://www.growingformarket.com/arti...-tomato-plants
Ihadn't reliazed that trichomes are also found on stems and fruits, not just on the upper leaf surface.
And yes, it is thought......that they might be more studied in terms of disease tolerances.
An additional suggestion.
There are specific know attachment sites on the upper leaf surface for the more common fungal foliar pathogens. Molecules of chlorothalinol ( Daconil, Bravo and friends) cover those attachment sites helping to prevent pathogen attachment and infection.
I don't know the structure of those attachement sites, no one does as far as I know, so might one suggest that there could be a whole family of structurally different trichomes, and also present on the leaf surface with different areal densities.
I'm not sure I'm explaining this well, but could try again later if it's not making sense.
Carolyn