Their care will be pretty much identical in terms of housing, temps, and feeding. YOU WILL NEED TO HOUSE THEM SEPARATELY!! The king may very well make a meal of the corn if housed together LOL!!
While at the show, dont be afraid to ask questions. For a first time snake like a corn, the issue is usally a matter of price for the first time buyer. You will see a myriad of corn morphs from normals on up, and prices ranging for $15-20 upwards to several hundred $$$. If you dont understand about a morph or costing, just ask whats the difference. Most vendors will be glad to answer questions and some may have pics of the adults. Ask to handle the animal. Most vendors will allow it if they sense you are a legitimate buyer and not just a "hawker" out for the day looking to play with cool creepy snakes and stuff with no intention of buying. Keep in mind most vendors produce many babies to sell. So, these baby snakes are not necessarily handled on a consistent basis. I have had calm snakes at a show turn into little devils once home and set up in their cages!! This is where the new love usually dwindles rapidly for most folks. The new keeper is afraid and doesnt even want to stick their hands in the cage to clean, feed, or provide fresh water. If you have too, put a pair of gloves on and go for it in a gentle and calm manner. Baby corns and kings are usually only capable of a tiny pinch or peck to us adults and MAY produce a bit of blood on a child. Still, relatively painless except mentally LOL!!
If you see two vendors selling the same corn morph at much different prices, ask why!! Sometimes the lower priced animal is a non-feeder/picky. Sometimes it is a deal and the vendor just wants to move them out. Seek out reputable vendors. Its too easy to find a good animal feeding reliably on frozen thawed pinks to take a chance at saving five bucks IMO. With both the snakes you are considering to buy, I doubt you will have any problems finding a good feeding animal that will make a great pet.
Also, be open to buying a young adult animal. Many breeders sell their young adult males that they no longer need or have replaced in their breeding programs. These are usually priced reasonably, feeding well, are tame and have been handled more, and you dont need to switch cages as they grow.
Good Luck!!