Why do people prefer pre-paid over plan...and vice versa

Plan, because you're never caught in a bad situation with no credit.

l guess it has something to do with your income.

l do not think anyone PREFERS pre-paid.. That is just all they can get. Bad credit, no credit, not legal citizens.. Etc.
The only good thing about Pre-paid is that you do not have to worry about being on a contract like you do with plans..
To get out of a contract.. You have to pay a really expensive fee that is about enough to have paid your bill for 3 or 4 months.

Because plans are freakin' ripoffs and you're stuck in them for God knows how long. If something happens where you can not pay your bill, you're in a heap of trouble. Plans are just stupid in every way. That is why they have to sucker you in with free phones.

l prefer pre-paid because l am not willing to pay interest on a bill the company may forget to send me just because l do have a credit card. Have had this happen to me for as long as three months before and really resented it enough to switch to another phone company and beat the charges they attemnpted to levy against me.. Plans just cover too long a span, especially when dealing with a newer, less established service

it depends on what sort of person you are.
i have a plan because l know l can keep to my limits, but in the back of my head l know l will ALWAYS have credit if needed.
but, if you spend too much on your phone then prepaid is good to help you stick to your goals (and not spend as much!)