Why the lower monthly payment isn't always the better deal
It's tempting to compare two loan offers by their monthly payment alone, but that number is shaped as much by the term as it is by the rate. A loan with a lower rate but a longer term can easily cost more in total interest than a loan with a higher rate but a shorter term — the monthly payment being smaller doesn't mean the loan is cheaper overall. This tool computes total cost for both scenarios directly, which is the number that actually answers "which loan costs less."
What to actually compare
Three numbers matter, not one: the monthly payment (does it fit your budget), the total interest (the real cost of borrowing), and the total cost (everything you'll pay, combined). A loan that wins on monthly payment can lose badly on total cost, and vice versa — which one matters more depends on whether cash flow or total cost is your bigger constraint right now.