It's cheaper than the organized bridge, and you rest for 40 minutes while crossing, it's fine if you're traveling by your own car, you drink tea and watch the sea and cross the street, there's a discount from 22 in the evening until the morning
If you have no time problems, if there is a bridge, it is always the reason of preference.. A delicious sea air, seagulls... not to mention relaxing by eating toast on a ferry with a car instead of driving..