The other side of the valley is definitely higher in price than the Quail Ridge / Via Roble area. There are larger homes and flatter lots in Happy Valley and it is generally considered to be superior. Some noise from 24 can be heard up near where you are asking about. There is not a lot of inventory in both right now and more should be coming as we enter the buying season in the Spring. Let me know if you would like more information or help on either neighborhood or anywhere else in LaMorinda.
If I can help in any other way, please fee free to contact me, happy to help.