The only real difference is adjustment frequency: a one-month option can move every month, a one-year option holds for twelve at a time. The better question is whether to stay adjustable at all. Neither gives you a fixed rate. With either one you're riding the index up or down on that schedule, inside the loan's caps. When an ARM hits its adjustment, the smarter comparison is usually the adjustable path against a refinance into a fixed loan. If a low-cost or no-cost fixed refinance is available at a meaningful discount to where your ARM would reset, locking in that certainty tends to be worth more than fine-tuning the adjustment frequency. Adjustable indexes can sit above fixed rates depending on the yield curve, so staying adjustable isn't automatically cheaper. Loan size matters too: - On a small remaining balance, a rate swing against you costs little each month, so you can afford patience. - On a large balance, the same swing is real money every month, so protection carries more weight. Nobody can promise which way the index heads, so don't pick based on a forecast. Compare the guaranteed cost of a fixed refinance against the realistic range on the adjustable, size it to your balance, and choose the option whose worst case you can live with. We're happy to run both side by side on the free Roadmap conversation.