Flights are super efficient, fast and not expensive in my experiences (obviously depending on time of year and when you book).
We opted for the ferry this past July from Athens to Santorini. Blue Star Delos was the ship. I wanted my kids to have that "ferry" experience and they loved it . Pulling up to Santorini by boat is breathtaking. We were in no rush as we were spending 5 nights in Santorini. It is up to you what you prefer and the time you have . Enjoy either way it is a beautiful island. We stayed in Perissa Beach after reading all the trip advisor reviews and we loved it . Even in July,it was crowded but manageable. There are many experts on the forum that give amazing advice!
Just be aware that the total trip time (check-in, waiting for luggage etc.) makes the total time not that different. Nonetheless, for a straight shot ATH - JTR, I'd fly ( did fly)
Flying is the way to go IMO. The ferry was neat but the 2-3 hour trip was enough. I could not imagine being on there for 7-8 hours. Again, IMO it would be worth the extra $50-$100 bucks to fly and save a full travel day.
Hi the ferry cost about the same as fight? I see one way two person around 130-140 euro.
That's too rushed for 10 days in my opinion.
You lose half a day each time you transfer to another island, by the time you pack-up, check-out, get to the ferry / airport and get to your next destination.
Two days is really one day of sightseeing.
Land in Athens. Fly directly to Santorini and recover from jetlag there. (Note: Oia is a village on Santorini - not a separate island).
Chose one other island. Mykonos is very popular, but Naxos may give more of a contrast. Read up on them both (or the other choices on that ferry route).
Leave Athens until the end of your trip to avoid any worries about flight / ferry delays prior to an international flight.