Definitely recommend the 2 day trip. In 2010 we went to Pamukkale and Ephesus (we had both been to Ephesus before but was still an amazing visit). At night we stayed in Pamukkale at a very basic
hotel (not ICR) and we walked around the park and huge lake on the other side of the Pamukkale pools - it was all lit up and was breathtaking. In the lake were hundreds of frogs singing away, surreal. Apparently many Turkish couples go there when getting married as its lucky (we saw many couples in their wedding attire that night).
We left the hotel early the next day to walk around the pools - was so glad to do this then as obviously as the day progresses it gets so hot there and there's no shade. Again another reason for doing the 2 day trip.
Ephesus is just an amazing place, the mere dimensions of it blows you away and they are still discovering more buildings etc! Well worth it in every way.
Chris