300 ft. is long enough that fiber will be the better choice if only to reduce signal loss. CAT6 has a maximum length of 328 ft., so while it would work, you're

300 ft. is long enough that fiber will be the better choice if only to reduce signal loss. CAT6 has a maximum length of 328 ft., so while it would work, you're going to have a faster, more reliable connection all around with fiber.