What do you want? Large eggs? A lot of them? Pretty eggs?
Best brown layers: American breeds like sex links, rhode island red, barred rock. A few others, like australorps and orpingtons. These generally lay large eggs, about 5 days a week.
Best white layers: leghorns of about any kind. In fact, white leghorns are the breed most often used for commercial production, but you can get other colors. Other Italian breeds like minorcas and buttercups are pretty good layers.
With exotic colors like blue, green, and chocolate brown, you won't get as many eggs. You can still get 3-4 a week, but they won't be producing as well as the ones I mentioned above. Some people say marans eggs taste better because of a different kind of protein, but marans are also expensive to get as chicks and don't lay as many eggs as the light brown layers.
Egg color doesn't determine healthiness. Each breed lays a certain color, and white eggs aren't healthier than brown eggs unless you do something to affect their health. The best thing to do for healthy eggs is to feed them a good feed, add in greens, keep oyster shell onhand, and allow them access to bugs. Some people feed their chickens flaxseed to increase the Omega-3 quantity as well. And I firmly believe that keeping happy chickens makes for better eggs because their bodies aren't being stressed as much.
Another thing to add: do you want to handle your chickens often? White layers are known to be more flighty than brown layers, though I have an exchequer leghorn chick that is always the first to come up and see what I'm doing. Orpingtons and australorps are super sweet. Rhode Island reds and barred rocks can be great pets, but some of them can be a little opinionated. My barred rock hen is sweet and quiet, and my RIR chick is already a bit gruff at 8 weeks old.
Edited by americanvalkyrie - 6/25/12 at 7:45pm