How are you planning to hunt them? Dogs, bait, spot and stalk? The general consensus is that spring bear will have much nicer fur (until they rub) and fall bears will be larger. If you are spot and stalk hunting, then later in the spring when the rut is started might give better odds as the boars will be wandering more looking for sows. Size varies across the country. I think the odds for bigger bears increases in some of the eastern states like Pennsylvania, but California produces some big ones too. I expect all states have some big bears, as well as the full range of other sizes.