Is the byakugan stronger than the mangekyou

no the byakugan can only let u see the chakra point of the target and see far distance
while the mangekyou let copy moves se the person attack
and when u make clones the mangekyou let u see the real person most off all the mangekyou can create a genjutsu called tsykouyomi and make jutsu called amatersu which can make black flames