how different can they be?

as the title goes..
what can be different..?
i mean like, not something that is different in few things.. but something that is totally different in almost everything..
let's see..
best friends..
they are like people who share almost everything.. have common ideas n etc..
but somewhere, sometime, sure there'll be a clash in ideas, opinions and thoughts.
how about couples..
some may say that, 'Oh, there's no such thing as different taste. he and I share everything. there's no differences in everything that we do.'
i don't really believe it when someone says it. Or perhaps I believe that, the couple had just got into relationship or never knew each other well.
this is because, man and woman are two different things.
If man was from mars then women are from Venus.
for instance,
guys might talk with all the vulgar words and etc. but the next day would behave like nothing happened. but other way around happens when a girl say something that is just rude to another girl.
the same thing goes with the way a girl thinks and a guy thinks..
usually a girl would think a lot before taking a decision. forecast the future perhaps.
but not guys. as long they can survive the day, then they have no worries.
this is not the only thing.. there's an endless list of the differences between a girl and a boy.

but this is not an excuse to fail a relationship.
all these differences are to teach us
 to understand each other..
 to compromise with each other..

 to be like a 'lock and key' or like a piece of puzzle..
where you be his strength in things that he's weak, and he'd be your strength in things that you're weak in..
and last but not least..

(1)to like the differences (better if i say, respect because, there's no way for me to like guys certain hairstyles especially the long hair! so respect it be..) hehe..
(2) to love each other despite the differences.. ^^