I don’t really consider running the coast as being offshore, but it’s just a terminology thing. I refer to running inside or outside as we have the ICW below NJ as an option.
I prefer running outside when the weather is nice, but it’s not always the shortest route. Whether or not it’s quicker depends on your cruising speed. With that, I see WAY more convertibles outside than I do inside. The reverse is true for motor yachts. That comes back to the speed vs distance thing.
By the time you run in/out of the passes, it kills any distance saved. Outside is just prettier and keeps you away from bridges, no wake zones, idiots etc.