I've raised Bresse for meat and eggs for a couple years now, they taste like any other home/farm raised chicken. Mine finished around 16-18 weeks the pullets start to lay around that time as well. I love Bresse good weight (4-6lb for pullets 6-8lb for cockerals)...
LF White Cornish or Black are very hard to find, might I suggest Facebook on one of the Cornish boards. The other colors can be readily found but if it White or Black Cornish stock be willing to wait for, I'm waiting on White LF Cornish myself....
I have Breese, haven't tried Dorking yet but my Breese takes 14 18 weeks to reach 4-6lb on average for pullets and 5-8 lb for males when i process them faster than most Heritage Breeds and they lay much better than my Marans or Buckeyes. Love my Breese.