They're all good choices, Scott. I'm not a big python/boa fan, so I'd lean toward either the corn or the king. I probably would favor the corn slightly over the king, for a couple reasons. One is that kings are cannibalistic and generally need to be housed individually. So if you should decide down the road to get a second one, you would have to invest in a second enclosure and another set of everything (water dish, hiding place, etc etc) . Corns, OTOH, can be housed together and will coexist. (As far as I know, anyway - my rat snakes have gotten along fine together, and they're the same genus.)
Also, while virtually all snakes are escape artists, kings seem to have more talent than most other varieties in finding their way to freedom. Not to downplay the escapades (sorry!
) of the others you mentioned, but whatever you choose, be sure you have a good, secure enclosure for it.
[bleep]e in a variety of species/subspecies, providing you with a large selection but a maybe a tough decision. California? Eastern? Florida (Brooksi)? Black? Mexican? and so on. Corns aren't much easier; they're all the same subspecies, but thanks to captive breeding there are more colors/varieties out there than Baskin and Robbins ice cream. Creamsicle, ghost, candy cane, etc. But that's all part of the fun! Good luck,
-----
MichaelB