Mothron Wings are ~81 blocks up flight, with no speed boost for horizontal movement. You've got about 2.67 seconds of flight time using them.
Hoverboard is ~86 blocks up, 108% speed boost for horizontal, and 2.83 seconds of flight.
By the numbers, the hoverboard is better. If you've got a spare plat after slaying the golem, the steampunker sells wings better than both, and probably the best wings short of Fishron or the four lunar wings.