I have a 2005 Maxxus and ran #6 all the way with a 60amp circuit. The total run from the main breaker box to the tub (including the sub panel) is appox 80'. Unless you have an extemely long run #4 is kinda over kill. But, thats all up to your electrician and codes.
I would reccomend going with the 60 amp circuit if you can. I live in Central Coast California and the temps are mild, but, I find that we always end up running 2 pumps while soaking. Wife sits at one end while I'm at the other.
Good Luck......
Karl