Every longbow I have ever owned has been 64", I even have a 64" recurve. I have had good friends do studies on them, and they determined a 64" bow to be the ultimate length to power ratio. So I went with their theory, and it hasn't failed me yet.
That being said, ask someone else, and your going to get a whole different answer.
Pick what you think shoots great, feels good in the hand, and last but not least, looks beautiful to you. Only you will know which bow shoots the best for you.