You're right .. for most it's probably better just to determine what's disposable and send that against the debt. But, once you send that, it's sent, you're not getting it back. The LOC is revolving so it gives you a 'take back' if for some reason you wanted it.
The other difference is you're no longer liable for the monthly payments to the loan on schedule and the payments to the LOC happen automatically when you transfer your income to it. And the interest on the LOC is 'average daily balance', so the act of parking the income against it throughout the month drives the interest cost down, as opposed to letting those funds sit in your checking/savings until they are 'ready' to send against the debt. Effectively every dollar you have is working against the debt every day of the month, and at the end of the cycle everything you didn't spend (or want to leave in there) is against it (and you can pull it back if you want). V.s. calculating that out and sending forever. So it's a way to pay off a debt as quick as you want, or don't want.
It's nice to be debt free.
I'm never borrowing again...