It doesn't matter what WE say.. getting familiar with YOUR market is KEY..
More than that.. WAY narrow down the breeds and work with only those which
YOU absolutely LOVE.. My true suggestion!
I thought Speckled Sussex were lovely as well.. they don't sell for CRUD here.. while PURE colored Silkies sell ALL day long EVERY day. French Marans also sell well. Lavender anything SEEMS popular.
I tried to find a jubilee/speckled Wyandotte.. looks like calling them Milli fleur in Europe though it has the mahogany base.. couldn't figure how to make them myself.. so TRYING to make "Isabella" laced Wyandotte from my lavs cross black laced red.
I voted for Isabella Leghorn.. though I'd be SHOCKED if you could get it AND also have it for sale in the near future.
I worked with white faced black Spanish.. FUN birds, very Leghorn'esque, good layers and foraging, challenging hatching. Screamers at harvest time.
Happy adventures!