It depends entirely on your preference and your snake. I have my 3 month old BP and my 13 month old corn: the BP eats outside her cage because the decor would get in the way otherwise and I find it easier to do since I clean her cage while she's eating. My corn, however, was raised being fed in his cage and will not eat outside...so I had to modify my techniques to fit what he was used to. Maybe some day, once he's used to handling, I'll get him to eat outside so I can clean his tank easier, but for now I have to do what is best for him to keep him healthy.

Bottom line: If your snake is more relaxed and doesn't care where it goes as long as it gets food, you can feed it outside for peace of mind. If it's really shy, doesn't like handling much, or is one of a large collection then leave it in it's home cage.