The DS18B20's are calibrated to 0.06 degree C. Have a look at their datasheet:
http://lomza.czad.org/pliki/DS18B20.pdf
There's probably a copy on the dallas semiconductor website as well.
I checked the four that I received and they were all accurate to 0.06 degrees of each other. I doubt that you could match that with an analogue sensor without going to a lot of trouble.
Bird