I too was looking at the Mavi Belci, but mainly over the hotel Karbel rather than the karbel sun. We stayed at the Karbel last year, and it was a lovely hotel, I did look into the Mavi as it was such a good rate, but in the end Ive secured the Karbel for less and because it was such a nice hotel we wanted to go back.
Is there any reason why you are comparing these two in particular? You may want to check out the Karbel (fab reviews on here!) and its opposite the karbel sun.
The Mavi will be according to the map a little closer to the sea, but the Karbel is only a 10 min walk down to the beach if that anyway, Olu is a lovely place, and we loved it so much it will be the first time we've returned to anywhere we've been before
Karen x