Although care & feeding for Kingsnakes is "generally" the same, each subspecies is unique, and has its own traots and dietary needs. (Speckleds seem to be the most aquatic, eating frogs more often than other subspecies.)
Some subspecies prefer lizards & snakes, and will reject rodent food if they have any choice. Best to avoid them:
Mountain Kingsnakes
Gray-banded Kingsnakes
Mountain Kings are also from higher elevations, and are prone to hibernate earlier than other species. In the wild, they are only active about 3 months of the year. Plan accordingly. The more southern the subspecies, the later in the year the specimen will be active.
California Kingsnakes are great snakes, I've had one, but they CAN be inbred. How do I know that? From the Labrynth variety that I had 2 years ago that was so pathetic that it could not even stalk and constrict properly. When it attacked the water dish, that was the last straw! (I've known other enthusiasts who have seen their Cal Kings try to contstrict rocks!!)
Young Cal Kings are also known to be more squeamish and timid that those of other subspecies. They tend to bite and musk more, too. As adults, however, they behave similarly to other subspecies.
It goes to figure that the variety that has been around in herpetoculture the longest has INDEED been inbred the most, for color and other traits. If you can get a spirited specimen with strong hunting skills, then don't hesitate. Much depends on the breeding stock.
Less common varieties, like the Mexican Black, have not been inbred as much. (They only became popular at about 1995.) My specimens seem to be somewhat more lively and have stronger instincts than other specimens I've had. (I've had 4 species of Kingsnakes.) None have had the crisp, efficient stalking and constriction techniques that my Mexican Blacks have demonstrated. They are also known for how well they handle, too.
Take your time, and based on diet and nature, get the snake that is best for you. For a beginner, I recommend one of these, in order:
Mexican Black King
Eastern Kink
Desert King
Cal King