My chicks are 2 weeks old today. I have equal numbers (5 pullets each) of BR, WR, SLW, RIR and black sex links (plus 2 RIR cockerels). Got them from Ridgeway Hatchery. The BR are by far the friendliest and most curious. The sex links are the least friendly/most scared of me. Also, they dont seem to be growing quite as fast as the others. The others all act about the same. Nothing earth shattering here. Just wanted to share my observations thus far, FWIW.
I have 1-each of BR, RIR, and sex-linked. Barred Plymouth Rock - Dumpling I agree that the BR are the most out-going. Dumpling is already a little snuggle chicken. She's only 3 weeks old but settles right in as soon as you pick her up. She's filling out well. Rhode Island Red - Nugget My RIR is the most aloof and whiney of the 3. Anytime we pick her up she complains and makes a big stink. If we're holding her with another chick, she's fine. I was told when I got her that RIRs are known for being "talkative" chickens. Nugget is going to be a hefty hen. She and Dumpling fight a lot and yet she can be very timid. Sex-linked (mine is black) - Gwenevyre Yes, she's the smallest of the 3 but also the bravest and most inquisitive. She was the first to jump out of the brooder and is always anxious to be with or near me. She has a very sweet temperament and is generally the first to do nearly anything.