Atlantica Princess - WITHOUT A DOUBT!
I've worked with both of these hotels and though Doreta Beach is an 'ok' hotel i've heard several complaints - mainly because it can be a bit 'Butlins' in terms of the entertainment, crowd it attracts, etc. It's certainly not a bad hotel if you get it at the right price.
Atlantica Princess is in another league. I chose this above all other properties i worked with when my parents came to visit (i was living in Ixia at the time), it's one of the best. It's also closer to Rhodes Town if you fancy exploring the capital, taking boat trips, etc.

i have been to the doreta beach and would not go back ever , mainly because there isnt much to do outside the hotel and although its got a large pool there is no shallow end, so if like me you have kids its not a good thing.

mandy