You know what, I don't have much experience with different breeds (4 at present time) or lines, but from what everybody says I am pretty totally positive that LINE makes as much a difference as breed in many cases, for temperament and for laying ability. This seems to be extra-true for very popular things like barred rocks or EE's (blue/green egg layers).
So it seems to me the first step would really be to figure out where you're likely to be choosing chickens from, and then try to find out as much as possible about the temperament and laying ability of those particular lines.
If you can find people in your area, or within an acceptible drive, from whom you could buy chicks or older birds directly, that would be ideal because you could (hopefully) visit and actually see what kind of temperament the parents have and talk with the breeder about how well they lay.
If OTOH you will be ordering from a hatchery, figure out which one(s) you'd be most likely to use (including whatever your feedstore sources their chicks from, if that's an option you're considering) and then take a poll here on peoples' experiences with your preferred breeds
from those specific hatcheries.
The weather thing is not really as big of an issue -- pick decent-sized things for cold weather, rose or pea or cushion-combed rather than single-combed if you're extra worried about frostbite, and either make sure to provide some way for them to keep cool in the summer or don't pick *really* big *really* deeply-feathered breeds if there is no way to prevent things from getting fairly hot in summer.
How many eggs do you want per day? And from how many chickens, i.e. how economically do you want your eggs produced?
Be aware that egg production may on average be lower in some of the obscure heritage breeds (than in breeds that have had some commercial production history (BR, RIR, white rocks, etc). Before everyone gets their stompin' boots on, please note I said ON AVERAGE, not all of 'em
If you want *truly* high egg production, like an egg nearly every day nearly all year round except during molts, you may need to look at specific lines of barred and other rocks, RIR, or at sex-links. I am sure there are some lines of some other breeds with similar production as well - but I guess my point is, if that's important to you, you'll have to actively seek it out because it won't happen from just any ole chicken.
Have fun,
Pat
