The statement that best compares the source of ethnic tensions in Myanmar and Cambodia is:
"Myanmar has tension between the Burman and the many Indigenous ethnic minorities and Cambodia has tension with people from the neighboring country of Vietnam."
This statement accurately reflects the ethnic dynamics in both countries. Myanmar experiences significant ethnic tensions primarily between the Burman majority and various Indigenous ethnic minority groups. In Cambodia, while the Khmer majority primarily experiences tensions with its Vietnamese neighbors, there can also be internal ethnic dynamics with Indigenous groups.