Santorini- visit Oia first or last?

Celebrity Equinox is supposed to be in port from 10:00 am to 8:00 pm on Sept 1, 2016. Most private tour companies seem to pick you up in Fira and then go directly to Oia and then continue with a tour of the rest of the island. We are looking at a 5 hr private tour with Unique Santorini Tours that starts in Fira but goes to Oia at the end and then returns you to Fira. Assuming that we start the tour at 11:00 am, that puts us in Oia sometime in mid-afternoon. Is this smarter than going directly to Oia first? From what I can gather, 2 other ships will be in port earlier than us that morning, at 7:30 and 8:00 am, while 2 others only arrive at 4:30 pm.

If on a tour, we do not think it makes a difference. When we on on Santorini, since we are always on our own (sans tour) we normally try to be in Oia for lunch...since we enjoy the more laid back atmosphere (and views) of some of the Oia restaurants. There are those who also like being in Oia for sunset....but this is not an issue on your cruise since sunset would be after 7:30pm...

We would add that we have viewed sunsets on Santorini from both Oia and Fira (over many years) but the best sunset of all was actually from the hot tub on a high deck of the old Star Princess (later converted to a P&O ship). We sat in the hot tub and watched as the setting sun played all kinds of shadows and colors on the cliffs of Santorini and it was truly magical.

Hank