Is dua better at graves or in a mosque?

Shaykh Faraz Rabbani (Allah preserve him) said,

“The default is that duas are answered. There is nothing decisive whether they are more likely to be answered in a mosque or at a righteous Muslim’s grave, though we do know that a believer is more beloved to Allah than the Kaaba itself (let alone any other mosque), by authentic hadith of the Beloved Messenger of Allah (Allah bless him and give him peace). And Allah knows best.”

Source: SunniPath Answers

Also see: SunniPath Answers - The Etiquette of Du’a