I was studying OSPF and this came up from a training material,in which the instructor says:
"in turn a loopback interface's higher level of stability and availability results in fewer SPF recalculations. which results in a more stable network overall."
there's no doubt about the higher level of stability and availability over physical interfaces, I mean for the sake of kinda connectivity and to make sure the device/router is up and running, physical interfaces could go bad easily and could make us some problem,but for loopback it's a different story,the only way for loopback int to be unavailable is for it to be manually deleted or for the entire router to go down. but how possibly using or not using loopback could affect SPF calculation??