Vueling Airlines or Aegean airlines

I've flown Vueling Airlines 2 times: Rome to Paris and Florence to Paris; nothing to report, just follow their rules on the baggage and don't select a seat in advance if you don't want to pay to do that.

No experience with Vueling but used Aegean a couple years ago from Santorini to Athens. They are fine. Remind me a bit of Southwest.

I have flown with Vueling several times. Overall the flights were fine. On a flight from Barcelona to Marseille many passengers were delayed due to extremely slow passport control checks and the crew informed everyone already seated that the plane would be delayed for a short time to wait for delayed passengers. We made up lost time during the flight and arrived on time.
Vueling did cancel and reschedule one of our other flights, but we have also had this happen with Lufthansa. We will be happy to fly with Vueling on future trips to Europe.

Thank you for info ... if you leave Croatia and go to santorini and stay on same airline but have layover in Athens or Rome do you have to pick up luggage and go thru customs

No - should be fine.

We flew Aegean from Santorini to Athens. We were very pleased with the service and price.

+1 for Vueling. I flew on Vueling in April 2017 from Granada to Barcelona and had a good experience. Planes are very new and clean, good service. The seats are just a little cramped.