Diamond Cliff was great. So many well-thought out luxuries, such as a little fruit stand, beach bag, and to-go towels in reception. Breakfast buffet was very good, and the shuttle was nice because it is on a cliff. We liked the pools, including the little underwater jets to rent. The slide wasn't as exciting as it looked in the pictures, but great for little ones.
The location was great. We weren't sure which beach to stay at, and went between Patong and Karon. We liked Patong's walkability and activities better. Kalim right nearby had a reef to snorkel and Patong down the hill had lots of activities and shopping. All the activities we booked had no trouble picking up from Diamond Cliff, and cabs knew where it was. Traffic is bad though, so if possible, pick activities that are near wherever you are staying, maybe doing river rafting from Patong and scuba from Karon.
A negative is they seemed to run out of towels and we got pool towels in our room for a bit. It also wasn't set up for 4 when we arrived, even though our reservation was for 4.
Out of our 5 hotels, Diamond Cliff is the one we definitely would book again.