Difficulty deciding on Greece/Adriatic itinerary, Viking vrs Celebrity

I currently have an Aqua class cabin on Celebrity Constellation booked for August 2018. We have sailed with them once before, and were very happy with our cruise. Just saw that Viking has a similar itinerary for the same, and with the half airfare promotion, I think costs will be about the same. This is the comparison:

Celebrity, 10 nights - Venice, Dubrovnik (overnight stay), Dubrovnik, At SEA, Crete, Mykonos, Athens, Santorini, Katakolon, At SEA, Venice

Viking, 8 nights- Venice (overnight) Venice, Split (Croatia) Dubrovnik, Kotor, Corfu, Olympia, Athens

I know we will be coming to Venice a couple of days early, either itinerary, and if we choose Viking, we will stay in Athens a couple of days.

I'm not worried about included excursions, drink packages, etc. that affect cost, thinking more about itinerary, and ship factors - which would provide the best experience? I also posted the same on the Vikings and Celebrity boards, which led to an answer to take the Viking cruise, then travel from Athens to Santorini. The most I could add on would be two to three days because of my work schedule. If I use the Viking air (50% off right now), I think I would have to fly out of Athens. The ship docks in Athens at 7am. I thought of flying to Santorini because it seems very inexpensive, but I don't know the logistics of getting to the airport, time involved to check in, etc. Is this even feasible?

I responded earlier on your post on the Celebrity board and have been following comments there. I think a lot of the Celebrity responders have taken this particular itinerary and loved it (and for good reason), but I'm not sure if all of them have been to ALL of the ports offered on Viking as well.

For that reason, let me give a little more detail why I think it's a better itinerary (even given the 8-days versus 10-days):

-- It's better to start in one port and end in another, to get a better sense of two significant European cities rather than just one.

-- Dubrovnik, while a LOVELY town, doesn't really require an overnight. I have overnighted there and while it's scenic, it's also somewhat dead at night; at least when I was there.

-- Chania is really nothing above average -- a little Greek town with a nice harbor; not much to do. When you compare it with Corfu, which is offered on the Viking itinerary, there's a certain similarity but Corfu offers a bit more in terms of scenery and in terms of the lovely Corfu Town.

-- Split is a very nice addition to the Viking itinerary. It's very different from Dubrovnik; the entire town is basically built inside the ruins of a Roman Imperial palace from the 4th century.

-- Santorini is of course unique. But what hasn't been mentioned is that it can be absolutely overrun with tourists when there are 3,4, even 5 large ships in during a single day. If you can swing visiting there after, from Athens, I think it would be a better experience all the way around.

-- Kotor is also very unique in a different way: the sail-in is absolutely gorgeous.

In the end, you'll have to decide what works best for you. But don't short-change the itinerary on the Viking sailing. It may be helpful to think of the Celebrity sailing as more Greek-island focused while the Viking one is more Adriatic focused.

Thank you for your input. We are waiting to hear from our TA to see how pricing falls out, and the logistics of Athens to Santorini. We still go back and forth because we love the sea days, and we have an aft cabin with a huge balcony, and adding on does cost more. But we did decide that no matter which we choose, it's going to be a fantastic vacation.