请问the reason that ...is that 和 the reason why ...is

The reason why he comes here is that he want to visit the
Great Wall.
The reason that he gives is that he want to visit the Great Wall
两者都引导定语从句，如果用why连接说明从句里句子成份齐全，不少主语和宾语，或者谓语是不及物动词如例1那样，只要用why做状语就可以了。如果用that 连接就说明此时从句里少宾语或者主语，例2中就是用that 做gives的宾语

貌似没有
the reason that...is that...

no difference. but "the reason that ... is that" is more comman.