1. If you sell your btc to repay your loan, you will have less bitcoin, and more cash month by month to buy btc.
2. If you take a loan with btc as collateral to pay back your debt, you will have all btc, and still more cash month by month to buy btc, if you take a repay at maturity loan (no monthly payments.)
In theory, in option 2, you could roll over your loans infinitely, so you never have to sell your btc for fiat. But in this scenario, you will have to have a bigger stack, so you can post more collateral if btc hits bottom. So this scenario highly depends on your stack size to begin with. With too small stack, I would not do it. Also questionable if you can roll over infinitely.